Yes, I have 10g over cat5. I don't need it, but I have it.

Ethernet specs are for cabling in dense conduit. Most people don't have dense conduit in their house. Much cable tests better than the rating on the jacket.

I am using 10G over an ~15m 4 twisted pair phone cable (PTT, common in France even decades ago for ISDN, but no cat cable at all) and don't remember seeing a frame lost in quite some years.

802.3an officially gives you 10G on Cat5e (and plain-6) up 55m; 6A gets you to 100m.