Except for the 3090, all gtx/rtx cards have discontinued use of the sli port. So you might as well say sli was now firmly a dead subject. That leaves the purpose DX12 was built for, multi-gpu (mgpu) and to date that's a dead end, 99.9% of games don't support mgpu and the ones that do support it, do so miserably.
Physically there's very few physical cards that are x16 and have a pin requirement other than gpus.
So the only way that port will ever get used is if you had a 'brain fart' and decided to seriously chop your gpu output by putting your gpu there instead of the primary port, which I don't see as happening nor plausible.
Your OCD I can do nothing about, same as I can't fix mine, so I fully understand that implication, so as...