It would, but it wouldn't be able to push 100gbs. It's not lying

I'm just looking around for this mystery 100 Gbps card. Think it'll work with Cat9?

Did you think this was made up for some reason? 100Gb cards are not new. QSFP28 was created in 2014.

https://www.broadcom.com/products/ethernet-connectivity/netw...

They don't use copper, they use fiber. It wouldn't be a mystery if you searched for '100gbs pci ethernet'.