Is there any evidence that theres really no difference?

You can't have true evidence for something as subjective as that, it might as well be a matter of opinion, but I can share some of my personal experience with this, if it is of any help; one thing that is very clear to me is that it can be very difficult to enjoy sex after you went a whole life without it, and by that I don't mean to say that the experience is not enjoyable, but that your brain sort of blocks you out of enjoying it the way you should because it didn't had it at the right time. Sex is something that you are supposed to first have at the peak of puberty when your libido is at it's sharpest; after you get older your sexual desire starts to decrease and it becomes harder to enjoy sex, specially if you go through depression as most incels do. If you have anxiety this can make sex even harder to enjoy as anxiety blocks out your parasympathetic nervous system which makes you inherently unable to feel pleasure or arousal. Add to that the fact you might have spent all of those lonely years masturbating to all kinds of fucked up porn and you have a recipe for disaster to your ability to feel pleasure from sex.

I am not sure if it has to do with people coping, or people getting too nervous and having that ruin the experience, which i think could be the case since many stories seem to be about it taking minutes to get an erection. So many years of social isolation has made their brains find self pleasure superior to partnered pleasure since their brains have concluded that they wont ever have a partner.

This absolutely happened to me. It took me two months with my first girlfriend to overcome my anxiety enough to have an erection good enough for having prolonged sex with her. The reasons were exactly my uncontrollable anxiety around her, as well as several years of isolation, depression, my lack of sexual experience, my reduced libido.

I never managed to actually ejaculate from sex by the way.

I see sex, to me, as somewhat like learning how to walk, something that normal humans simply do naturally with no effort at the right time. But we incels aren't like normal humans, we are more like a baby who was never allowed to stand up until the age of 30; who always had to move by crawling (in this analogy, satisfying our sexual desires by masturbating). Understandably, it would be a very difficult journey for this man to learn how to walk after his whole body had become so adapted and accustomed to crawling, specially since such a critical window in the natural progression of his life was lost.

I'm not hopeless about the whole issue though, even though I haven't really ever fully enjoying sex to the climax, I can still tell how my last relationship was better than my first one. I'm fully convinced that sex is something that, over time, you can "train" yourself to enjoy.