They didn't even link the setting in their email. They didn't even name it specifically, just vaguely gestured toward it. Dark patterns, but that's Microslop for ya

going to github i was greeted with a banner and a link directly to the settings for changing it

I've seen worse dark pattern to be honest... I don't think they're being malicious here.

They do not make it very simple to opt out. That is false.

On Android for instance I invite you to use the GitHub app and modify your opt-in or opt outside settings... You will find that nothing works on the settings page once you actually find the settings page after digging through a couple of layers and scrolling about 2 ft.