I also worked for Twitch and can confirm what you're saying is true. These repo's any staff member had access to - including non-engineering staff.

Revenue for the longest time was as simple as navigating to a streamers dashboard as staff, but they did finally gate that away from staff who don't need to see that info, however I am sure there are other ways to obtain revenue reporting info.

I am assuming all data - including personal - has been compromised but so far, the data leaked is data that most staff would have access to in some way or another. Some may find that shocking, but this was not a "high level hack"