Sure GTA6 may be a slight uptick in the amount of data being downloaded like any new game being released, but I would wager that the amount of data they are normally pushing out for downloads just on a regular basis (wether new purchases, redownloading games, game pass, etc) is already quite high.
If they roll it out evenly the week prior, then today (1/7th) is just 75 PB. To get that done in a single day would require a sustained 6.9 Tbps.
I'm sure this is all handled by a CDN at some level... but again it's not nothing.
6.9 Tbps to get it done in a single day is even 3x less than the minimum on Steam in the last 48 hours https://store.steampowered.com/stats/content/ and they don't even have GTA VI to distribute.