I'm sure the pagination might better for performance, but it's terrible UI.
Ctrl+F on a list of 10000 entries is far easier than clicking through 400 ajaxy pages and trying to figure out some custom and buggy filtering system that probably doesn't allow regex.
Past 10000 records most sites probably ought to just let you export in something bigquery compatible anyway - Regular Joe isn't going to have more than 10000 of anything, and anyone who does can learn how to use proper data tools.
Did you miss the part where I noted Github’s lists fail to load (let alone render) long before that point?
Edit:
Realized *.github.com takes you to your .github.io sites.
Wait, what? On iOS Safari I can only see repos in desktop mode now (except the issue tracker which is responsive anyway). Which is a good thing. Not sure why you have the exact opposite experience?
(I do vaguely recall being asked if I would prefer desktop mode on my phone a while back, and I said yes.)