张金羿, You are very welcome, we are glad to help.
"I consulted Gigabyte a few days ago but they haven’t responded to me yet, so I still have a few questions", perfect, that was the best thing to do in this scenario in order to confirm from their side what might be the source of the error.
"If this WHEA error points to a problem with the motherboard's PCIE interface, shouldn't my graphics card be unusable?", In theory, yes, but keep in mind that the error could be related just to a portion of the motherboard's PCIE, meaning that does not necessarily indicate that the graphics card will work or not or that the port is defective, it could be just an error related to it but that still allows it to work.
"Do I still need to contact my graphics card supplier?" Since the graphics card seems to be working properly, then we would suggest to wait for Gigabyte's response. Still, if you have the opportunity to do so, it is a very good option to try, maybe at this point to check directly with them if they have some sort of reports about this issue that could indicate what might the root of the problem in this case.
"The main question is, do I need to care about this WHEA error?" From what we know, based on what you have reported and according to the link we provided previously, the type of error is related to a hardware problem, and it could be any of the parts. Even though it seems the problem is related to the graphics card, one of the troubleshooting steps to try will be, if you have the option of course, to test a different graphics card on this same board, that will let us know for sure if the problem is, in fact, the graphics card. We understand that this option might not be always available, which is why it is a good thing, as you asked previously, to get in contact with the manufacturer of the video card to confirm if there is any further assistance and suggestions they can provide on this topic based on their card:
https://www.nvidia.com/en-us/support/
Regards,
Albert R.
Intel Customer Support Technician
