Earlier quoted context omitted.
> dealing with SSO is probably easier than handling passwords, reset flows, etc. It's really not that difficult. Yes you need to be aware of risks, and be more careful with the data. But it's not exactly rocket science, and you're never going to end up in a scenario where your users can't login because the login flow is out of your hands, as per the topic of this thread.
> you're never going to end up in a scenario where your users can't login because the login flow is out of your hands It's more likely that the person re-implementing the SSO flow is making a mistake and the login behaviour is getting messed up than the default Google/Apple SSO implementation that's deployed to billions of users and business critical for many companies that use that kind of SSO internally too.
The thread has other people confirming the same behaviour - and the description of the issue (preventing a double-submit of a non-idempotent action) is something most web-focused developers learn in their first year.
I don't understand why people assume that the people working at Google/etc are inherently incapable of producing bugs. Go literally invented a new programming language to make their staff less likely to fuck up because they don't have much real world experience: https://www.youtube.com/watch?v=uwajp0g-bY4