Why do gaming companies like blame P2P issues on NAT?

I work at a college, so I get to support home devices like game consoles and Smart TVs on an enterprise network.

From my understanding when you want to play online with friends, the game devs can either use a P2P connection where one player hosts the match and everyone connects to them or just a dedicated server everyone connects to. Games like Destiny 2 on PC and most console games will use P2P.

That's all fine and dandy, but those games will report to the user that they have "Strict" or "D" NAT level since they're behind a firewall that doesn't want P2P or support UPnP. My problem is that it has nothing to do with the NAT settings. My enterprise firewall doesn't like all these outside connections trying to get in. That's literally it's main job.

So why blame it on NAT? It was confusing for me and still is for my users.