SO if you flash your bios, you blow the fuse and they can tell you bios modded it to mine with it.
So by your statement it will happen only to amd users cause only amd gpus can be modded. So as long as gaming gpus can mine then nvidia is a safe bet cause there is no way they will say if it was used for mining or gaming.
They can't void warranty either way.
Say I write myself some OpenCL program that basically has a purpose to "Find the first trillion prime numbers...."
Its not a game... its not mining... will my warranty get voided?