I would bet money that Intel's dev rel team worked closely with Avalanche to add XeSS support to sell more Intel GPUs.

Most likely the Hogwarts devs were said, "sure, do whatever you want on your own hardware, just don't you dare break anything on any other platform while we're trying to ship". The easiest way to green light this and know nothing else would be affected would be to hard code everything behind Intel's vendor IDs.

So this probably isn't a case of Intel working around a game dev's code, it's probably a case of Intel working around its own code.