How does CalDigit Thunderbolt 3 Mini Dock support two displays from one USB-C port? According to the FAQ for the CalDigit Thunderbolt 3 Mini Dock, two different monitors can be connected in extend mode through the single USB-C port. How is this possible if MST is not supported?

Why can one not do the same thing with other USB-C hubs like this one? It says in their FAQ that one cannot connect two external displays in extend mode on mac because of lack of support of MST.
The clue is in the name: Thunderbolt and USB are two different things, even though they both use the same plug and socket. 

USB C offers some of the capabilities - video signal, power transmission, data; but Thunderbolt provides a greater range of data travelling down the same cable.

The Thunderbolt Dock has 2 HDMI ports, which can provide two separate video outputs. The USB hub has one HDMI port.