That's super duper grey area, which is why GPLv3 went out of it's way to have an explicit patent grant.
Re:exFAT in the Linux kernel
by bubblethink on Wednesday August 28, 2019 @05:15PM
(#20824041)
So the code in the linux kernel would have to be signed off/committed by MS in that case, right ? For a grant to have any meaning, the code would need to come from them ?
So my guess would be that the definition of "derivative work" would apply.