Let me retract my compatibility statement, a bit.
Seems that Gigabyte in their infinite wisdom decided to put two signal traces under one of the standoffs, so if you screw the block down it will short out those signals and GPU will not detect. At least in my case, I have first thought it was due to bend to PCB because in my case, GPU is 0,4mm taller then the flat plane for standoffs and i did damage the core\BGA balls, but when i dropped GPU back to original fan shroud, it works perfectly fine, ran stress test in 3dmark and furmark, no visible difference in performace\behavior.
So, what is the culprit? This pad at the top right:
I measured resistances, inner part is ground, the outer is part of some kind of power circuit (there is a choke and cap). Resistance between ground and the circuit is about 15Ohms.
I can see on the "older" PCB design, the outer edges of this hole are covered in mask (looks like):
Original fan shroud has quite tiny standoffs and are centered. The inner pad size is about 4mm and the standoffs have 3.94mm size, so it fits very precisely and does not short circuit:
I am lucky I guess the short circuit did 0 damage (I hope) and it was saved by some other electrical magic going around in there.
I will attempt to mask off the pad with kapton tape, all 4 of them to level out distances.
Also noticed they route PCIe signals around the bottom left one too, quite close to the mount. Seems it might get shorted too if the standoff scratches through the mask.
Well, should have listened and avoided gigabyte with all my might

.