I didn't find out I was autistic until I was an adult, but at no point did my parents tell me I couldn't wear masculine clothes or that I should be more feminine.

The problem with autistic women and girls is that a lot of the things that are expected of them is usually uncomfortable for them. For example, women's underwear is uncomfortable almost as an art form, and a lot of women's clothing is made from unpleasant or rough materials, whereas men's clothing is usually less form fitting, softer and usually more practical (movability, don't have to worry about skirt/dress revealing underwear, pockets). Not to mention girls/women are (non verbally) expected to sit a certain way, behave a certain way, say things a certain way, do things a certain way, which autistic girls and women aren't always aware of, me being one of them.