It's not covered by NDA as far as I could tell, and that part was pretty clear, basically says "if the game is sold on other platforms, make sure the price is the same". It's one of the first things you sign when making a Steamworks account.
Linkyu
I would add, there are at least two other cases that necessitate Unity
the first is, unity is also used to make software, not just games. anything that has a 3d element can just be made in or with unity. I'm talking AR/VR stuff, builders, simulators, etc. I have a friend who made training software for welders in unity, for example.
the other one is vtubers. while not strictly necessary, the moment you want to model something a bit more complex you will likely have to deal with unity because the vrm format has become the standard (note: very over-simplified)
although they're not necessarily game cases, they're related enough that I wanted to bring them up
the cows voted
alas, sepulchritude has been at an all-time low 😔
man I need to pay more attention to the posts' title now, I'm not used to seeing SRMG here and got caught so off guard thinking it was real
the smoke kinda looks like it's spelling "2001"