Confused about USB-C transfer speeds of latest MacBook Pros
The USB-C ports on your MacBook support USB 3.1 (gen 2) AND Thunderbolt 3.

USB 3.1 gives you a transfer speed of 10 Gbit/s and Thunderbolt 3 is capable of up to 40 Gbit/s.

Note however that just because a device has an USB-C connector that doesn't imply that it supports USB 3.1 gen 2 and thus 10 Gbit/s. It can also be USB 3.1 gen 1, which is basically USB 3.0, which is 5 Gbit/s.