I think this would allow anyone with enough information on an account to claim it to be their own and have it removed which puts GitHub in a tough spot, DMCA claims on the other hand have legal ramifications so this route is more difficult to abuse so easily, although as seen with youtube-dl it's still abused sometimes.
If all the commits on an account have person X's name on it, letting person X hide the repo isn't going to do much harm. And you can send an email to the account owner asking if they dispute the claim.
Yes, GitHub support is pretty bad. I have an alt account that I want to log into that I can't remember the exact <myemail>+<suffix>@gmail.com I used to register the account. They won't tell me what the email address is, I can't prove to them I made the commits on the account, no matter how much information I give them. The only recourse I have is to wait a certain number of years when GitHub classifies the account as dormant and then I can request the account be reclaimed due to it having the username I prefer (my name).
I completely understand the security reasons for not leaking any information such as the email address but come on, I already know the password to the email if I could send a password reset and every other related piece of info, etc. They won't even send a password reset on my behalf. All I ask for is the email address. I didn't activate any advanced security features like 2FA on the account.
In addition, they take around a week or more to respond to the contact form, so disregarding my specific situation entirely, their response time is a bit meh
