Mesh with one nRF52DK and nine Thingys explentation

This video presents how Bluetooth mesh network works . As we can see this network contains nine Thingys and one nRF52 DK (not nRF52840 DK).

I'm wondering about mechanism of connection and witch device is configured as server and witch is client in this case. 

Is it true, that Proxy client node is nRF52DK in this case ? What about Thingys? Are they Proxy server nodes? 

As we can see the Field applicatioon engineer in this video is able to choose first thingy or fifth, or eight or any in this network and control them.

I thing that Smartphone is connecting every time to nRF52DK in case when user want to send any data so DK is somnetking like gate in this network? Is it true?

Is nRF52DK entry point for each piece of data (for example commands)?