Are you thinking of the USB A yubikeys? The 5c that I linked has a shell around the connector. It seems no different to me than any usb type c or thunderbolt cables that I own.
Yes the A yubikeys indeed. That's the original yubikey, the C version came much later. And it's still pretty rare at our work so I didn't imagine the poster referred to that. Also because the A version is much more solid. The connector is just a plate and there's nowhere for dust and dirt to accumulate, unlike the C version.
