However, while reading, it felt weird that they treated Skipper as a third-party dependency, even though it is developed and operated by their colleagues. I mean, they could've tried contributing some updates and improvements to Skipper, maybe reusing Skipper's discovery mechanism, instead of rolling out their own, completely independent LB module.

And yes, it's true that in big companies it can be hard to organise cross-team collaboration, but IMO it's still worth a try.

this is interesting. these names dont look like aws regions. are they geographic divisions or groups randomly assigned to users? or based on something like total spend over last N months to make sure high value customers dont quit?

if users are assigned to a stable group that would mean some of them experience way more issues than others. i would do it with a random subset of AZs or individual accounts thats different every time. not sure which one is the case here.