[Off Topic] Deus Ex had a profound effect on me growing up, and probably shaped my views which last to this day. Unfortunately, very few games like that are made nowadays.
> Games have minimal dependencies re OS APIs wise.
Sure, if you exclude "let's use every little quirk and undocumented feature in the graphics and audio and input stacks we can find because gotta go fast sanic noises".
Both games and office software (ab)use OS APIs; the difference is the specific subset of those APIs said programs (ab)use.
So yeah, you're right that it ain't "bullshit", but don't write off games as somehow "easy" compared to office programs; a substantial amount of effort has been poured into reimplementing Windows' multimedia stack in Wine and continues to be poured even now.
DirectX9 is not easy at all, it's almost Glide/Vulkan like low level-ish API. But hey. that's "bullshit". My balls. The above user should try running a pure DX9 game with Wine and GL 2.1 on a Intel Mobile 4 series with no noticeable frame drops. I tried. Hard.
But also, having DX7/8 being almost 100% compatible back in the day was a huge step on stability vs Windows 98, even if the RAM and CPU usage were higher. DX run fast, so did Max Payne.