No, you're missing the point. This must be like the fifth post where I've stated these things, but you've yet to address a single one of them, so I'll put it in list format. For future reference at least.
1. A list of cars appears in Max Payne 3. This has been independently verified. I won't bother showing the links on the Internet, a simple google search will suffice. If the file were a fabrication, that would've come to light already. Other people have found the file. The file exists.
2. The cars are obviously GTA related because it there are names of past GTA cars like Infernus, Burrito, etc.
3. In addition to these cars listed, there are other vehicles listed.
4. Rockstar has been known to include GTA information on other Rockstar products, like Bully and Red Dead.
Now I shouldn't have to explain this to you, but you've demonstrated such a stubborn inability to comprehend this simple bit of logic that I'm compelled to spoon feed it to you. The file exists. The file contains cars related to GTA. In addition to these cars are other vehicles, new vehicles, suggesting that this list is for an upcoming GTA game. And to drive the point home, Rockstar has done this before.
Apply Occam's Razor. What other thing could this list be? No really, what other thing could it be? Because it seems to me that we've exhausted all other options. Cars scrapped for a past GTA game (then why the snow vehicles?)?
Before you respond with, "There is no confirmation that these are in GTA V." Yeah, no shit Sherlock. That's the very definition of a leak. We assess each leak on its merits. If you refuse to consider anything less than Rockstar themselves confirming it, then you're the parallel of all those noobs who believe every leak. Historically, leaks happen. And we have very good cause to believe that this is another instance of a leak.