Official internal chat will be either Slack or MS Teams. Using any unauthorised app to discuss matters relating to the business would be a contract violation.
Realistically, game devs do this all the time in private chats with colleagues that happen outside work, both online and in person. But of course R* either never knows about those or chooses to overlook it.
In this case, I suspect the fact they were unionising was the reason they actually took action on it. It’s not about consistency, it’s about having an excuse to fire these people.
We already know the affected workers were using Discord to organise. My guess is they were discussing work issues there, and Rockstar jumped on that as an excuse to fire them (as it would constitute a breach of NDA).
“Typically, when a customer purchases a hacked console or the circumvention services, Defendant preinstalls on the console a portfolio of ready-to-play pirated games, including some of Nintendo’s most popular titles such as its Super Mario, The Legend of Zelda, and Metroid games.”
Yeah, that’ll bring the hammer down every time.
We can argue about the legality and morality of mod chips all day long, but building a business on distributing pirated software (and software that’s still being actively sold, at that) is a legal slam dunk.