That likely just doesn't exist yet, given how iterative a process game development is.
It's all likely older footage and is absolutely internal development stuff, not some sneaky peak at a final, polished product. Based on what we've seen, yup, this sure is a GTA game in the works. The big dump of leaked footage may still be floating around, but unless you're extremely interested in picking apart debug footage you aren't missing much. Given that GTA 4, GTA 5, and both Red Dead Redemption games have had online servers, it feels like a must-have for GTA 6.
Rockstar is still regularly adding new activities, content, and events to its big multiplayer world. GTA 5's online Los Santos has yet to run out of gas. (Image credit: Rockstar) Will there be a GTA 6 online?