Most of us recognize that gender is different from biological sex. We just don't believe people should be defined by their biology and biology is irrelevant outside of a medical context.

Biological sex is irrelevant in most contexts, but it's still relevant in a number of situations outside a medical context.

For example, toilet facilities in schools, workplaces and the public sphere are designed and outfitted differently because males and females have different urinary anatomy and because whereas males only urinate and defecate in toilets, female people have additional physical needs and processes that we attend to there - menstruation, pregnancy, miscarriage, menopausal flooding, etc. Females can't use urinals, males can. Females need sanitary bins for soiled pads and tampons we use when menstruating, after childbirth and during menopause, males don't.

Generally speaking, females need to use toilets more often than males do due to menstruation, pregnancy, miscarriage, menopause, birth injuries, coz we developed hemmorhoids in pregnancy that nevere went away - and coz due to our different urinary anatomy, females get UTIs much more frequently than males do. Due to birth injuries and hormonal changes of peri menopause and menopause, many women have issues like urinary and fecal incontinence, chronic UTIs, bladder and pelvic organ prolapse...

It typically takes girls and women longer to use the toilet each visit coz we have to partially undress, sit down, wipe after urinating, pull up our drawers and put our clothes back on, sometimes wash off blood from our clothing and hands, etc. Also, coz females tend to wash our hands after using toilet facilities for any reason, whereas males don't.

When using toilets, girls and women are vulnerable in ways that boys and men generally aren't.

https://www.npr.org/sections/goatsandsoda/2019/09/20/762764826/how-to-design-a-female-friendly-toilet

Sports is another area outside the medical context where sex really matters a great deal. And not just in sports competition, but in more basic ways like the kit that's issued to the two sexes and the actions that each can and should/n't do. Boys and men doing various sports need jock straps and cups. Girls and women need sports bras and attire cut for female bodies. Females playing soccer need to be careful about using their heads to contact/control the ball coz due to differences in skull anatomy and brain fibers, females have a much higher risk of concussion. Males can train in the exact same way every day of the month, but females need to adjust their activity according to their menstrual cycles and pregnancy status coz changing hormone levels in females mean there are certain times in the month/life that girls and women are much more prone to various injuries coz of such factors as different levels of tension in our ligaments...

Sex matters a whole lot when it comes to PPE and safety equipment, too. Most safety equipment has been designed exclusively to fit male bodies and male faces and heads. Seat belts and air bags were designed, tested, instituted and made mandatory by law without anyone thinking how they would suit female bodies. Seat belts customarily cut into women's breasts and necks, and can't accommodate a heavily pregnant woman's belly.

Airline design is another area where sex matters. The seat belts don't work for pregnant women past a certain stage of pregnancy. The way seats are designed make it impossible for many visibly pregnant women to stand up and exit their own seats if the people in the row ahead have their seats tilted back. The toilets on commercial airplanes are very difficult to use if you're in the sixth month or beyond - especially if you're carrying multiples.

Sex sometimes matters in the workplace too. There are chemicals, conditions and other things (like X-rays) that women who are known to be pregnant or possibly might be pregnant unbeknownst shouldn't be exposed to coz of risk to fetuses. Sometimes this is the case for women who are TTC or breastfeeding, too. The design of machinery, work tools, office furniture, and the standard temperatures that indoor workplaces are kept at are all designed and calibrated for male bodies and male attire only. Also, women who are BFing need a private, sanitary place and work breaks to express milk and store it.

Sex matters when it comes to figuring out life and car insurance rates, as any actuary can tell you.

Sex matters when it comes to policing and prison facilities. Males and females have completely different offending/criminality patterns.

Sex matters when it comes to nutrition and food costs. Food shopping, cooking and budgeting for food costs in a household made up of 5 males and 1 female will be very different than if the numbers were reversed.

Sex matters when it comes to population planning. Women tend to live longer than men, so there needs to be more suitable housing accommodations and senior services for elderly women than for elderly men.

I could go on with many more examples.

Sex is assigned on our birth certificates based on observations.

Sex is determined at conception and develops early on in utero, and it can be ascertained with 100% accuracy in utero - as early as 8/9 weeks with CVS and the NIPT, later through amnio and sonograms.

At or shortly after birth, midwives and physicians observe and record a child's sex on medical records. In most countries and US states, births must be registered with the appropriate government body within a certain time frame following a birth - in most US states, within a week or less. In England, Wales & NI, parents have 42 days to register a birth; in Scotland, it's 21 days. But only after a birth is registered with a government does the government issue a birth certificate.

However, not everyone in the world has been issued a birth certificate. And for many who do have BCs, there is a huge gap between the time of birth and when a BC is issued. For example, Caster Semenya wasn't issued a BC until Semenya was 16.

I hope your throat is better. When you're up to it, I hope you do some research into the areas you keep spouting strong opinions about coz you're coming off as very poorly informed about the actual facts and complexities.