I said USB-C which covers solely the connector. I've got USB C ports on my monitors which also work as DP inputs with a DP to USB C cable.Actually, the USB 3.x standards, which use the USB C connector, do specify the bandwidth.
AIUI Thunderbolt 3 requires active cables.
Indeed I did miss that point; you might have tried mentioning it straight off! Clearly I had not had sufficient tea.