[bipson]

You guys are talking about the same thing (and on the other side, not, but you don't realize how): Thunderbolt 3 uses USB-C, because USB-C is the connector spec.

If I understood it correctly, Thunderbolt at the same time can "carry" USB. So basically if you have Thunderbolt 3, you also (potentially) have USB.

A non-Thunderbolt USB 3.1+ USB-C can via Alternate Mode (depending on devices and cable) carry e.g. a DisplayPort A/V Signal over dedicated lanes (but has not nearly the same Bandwidth as Thunderbolt, so restrictions apply).

So: "Every Thunderbolt 3 is USB-C, but not every USB-C is Thunderbolt 3".

Yes, it can get confusing, but essentially you both are arguing about A is better than A, because Thunderbolt 3 uses USB-C. The "fullest" features set though you only get with Thunderbolt, for now at least.