You should not be allowed to sell USB-C cables that aren't USB 3.0 (5Gbps) capable w/o VERY clearly labeling as such in the title AND on the actual cable.
I bought a USB-C "charger cable" made by Anker, and burried in the specs is: Data Transfer: USB 2.0, 480 Mbps, but no where on the cable is it so labeled.