Back in 2001, ATI got in some hot water after it was revealed that they intentionally blurred all textures (used a lower resolution mipmap) if you were running Quake 3 Arena. Changing all strings from "Quake" to "Quack" (including renaming the executable) disabled the degraded mipmaps, and improved the graphics (and reduced framerates).
https://web.archive.org/web/20190728022442/https://techrepor...
Meanwhile today, graphics driver tweaks for specific games has become a regular feature and is advertised in the driver release notes (and I guess that's one reason why graphics drivers have become so massively big).
I can't remember where I heard this from but I remember a talk from some guy from the DirectX team and he said that so many games use completely illegal and unsupported/weird API options and calls.
He said that's what 99% of the game optimizations are. Putting stuff in place to fix broken API stuff.
This is true. I am a graphics driver developer and part of my job is to debug rendering issues in games and we often encounter spec violations in the game. Especially so in the era of DirectX12/Vulkan explicit APIs which shift the responsibilities to the developer. Most common culprits are missing resource barriers (image transitions in Vulkan) and uninitialized resources (color/depth resources for the most part require explicit initialization). The thing about those issues is that they are likely to work on one vendor's GPUs, the one that the game developer is using, but break more or less catastrophically on another vendor's GPU.
Also it's not easy to get them fixed in the game, because of the realities of engine update cycles and things like console certification process. Unless you report the issue several months before release, there is a slim chance you will get a fix in the game.
So game companies release broken code and it somehow becomes the world's responsibility to fix it... Sometimes I wonder if simply allowing these things to break for once would be a good thing for the industry.