I would classify that as access to production systems.
The other access rights that come from staff access is either incedential or miss /debt in architecture.
"Hey, pick through everything I say with a fine-toothed comb and treat it as the official company stance!"
I suspect that's a lot more controlled these days, but it wasn't very uncommon for signified staff to be trolling along with everyone else.
The leak includes source code of multiple active websites and applications that are operated under the umbrella of Twitch/Amazon.
Why would an intern have access to this data?
If you're saying that Twitch runs their developer environment in a lousy manner (and you have proof of this), then please go ahead.
But to imply that an intern/average developer would be given access to all this branching information is ignorant.
Maybe the super secure siloed world doesn't really exist outside of military/government organizations.
monorepos are a thing at several companies (e.g. Google).