Well, USB 3.1 has a max speed of 10gbit/sec.
Thunderbolt-3 has a max speed of 40gibt/sec.

If the Thunderbolt port is using a USB-C connector, then sure.
If USB 3.1 or USB 2.0 is using a USB-C connector, then no.

It is all about the electrical protocol being used, not the connector.

EDIT: So a more correct statement would be "Thunderbolt-3 has a max of 40gb/sec, using a connector that conforms to the USB-C connector standard."

When being used for Thunderbolt-3, that port on the XPS-13 is a Thunderbolt port, not a USB port, so referring to it as USB-C creates confusion.

When that port is instead being used with USB peripherals, it is a USB 3.1 port, with a USB-C host connector.

The notebook's chipset can electrically switch modes from USB to Thunderbolt or DisplayPort, depending upon what is plugged into it.

Cheers