I have been researching into this mmWave technology and its quite impressive. Was about to buy this mmWave SEN0395 device as it looks to be much better than the RCWL-0516 i have.
I was interested in mobile.andrew.jones’s question. I found a paper that says the EU and US regulations are phasing out the 24GHz band in favour of the 60GHz. This started in 2018 and:
As of Jan. 1, 2022, the 24-GHz UWB will no longer be allowed for industrial use in
both Europe and the United States
This seems the reason for the aqara device using 60GHz.I know this si for industrial use, but i can only assume other uses will follow suit. It seems that 60GHz is slightly better, with “16 times the available bandwidth once the regulations take effect”. So that seem good
I also wonder if 24GHz would interfere with other devices going forward. So, i may wait for a 60GHz mmWave device to be released. Seems the first time playing with esphome and sensors i have hit the bleeding edge tech, so will wait and see what comes out 
. Still tempted to get this 24Ghz device anyway to play.
Source:
https://www.ti.com/lit/wp/spry328/spry328.pdf?ts=1643270730752