So, as silly as it sounds, there are three things in that video that convince me there's an actual game there.
1. The sheer quantity of numbers on display. Like, it's a ludicrous amount of exposed stats and numbers. YMMV on whether that's a good thing in a game, but I struggle to believe someone just throwing together a mockup would make one with such information density. It'd be sparse and pretty, less effort, right?
2. He frequently gets distracted by new menus or popups, cutting himself off mid-sentence to explain them. I wouldn't expect this from someone showing off a fake, they'd have a tight script written beforehand.
3. Birds. Yes, birds. It's a completely unnecessary graphical feature that nobody would have noted the absence of. A total waste of time for a scammer, but something a stressed out coder might well spend an hour or two working on to unwind.
My main concern now isn't that the game will never release (although I have no expectation of another video coming next week), it's that he's going to suddenly dump it into full release and it'll be impenetrable. Multiple reworks and years of tweaking by one person, with little/no feedback from anyone else isn't really a recipe for ease of use, or even legibility when so information dense. Here's to hoping it goes the early access / open beta route and he's receptive to feedback.