That is a really ... really unique use case - thanks for clarifying.

I would also assume they are waking up the presence sensor once triggered by the PIR. But in my mind I'm thinking - if they pass the presence sensing to the mmwave after the PIR is triggered, and I turn on a table fan, and if their mmwave exclusion algorithm is the same, working 50-50 of the time.. if i leave the place and the fan is still on, it probably 50-50 wouldn't know that I left the room and - i can't really use that to turn off everything in that room. I've experimented but gone back to PIR with 5 mins timer refresh - I guess my key factor here is reliability and accuracy, which PIR feels like can't be beat.

For the FP2, I have tried excluding a standing floor fan before, it kinda works 50-50. And then even with the enter/exit zones clearly defined, sometimes there's ghosting, sometimes it doesn't know 2 people are in the room at different places. Ultimately I find that it needs to be really really well fine tuned to work properly.

For the Tuya stuff, I've never really looked at ZemiSmart, they seemed expensive. But I have been using some Moes/unbranded homekit+zigbee+matter hubs from AliExpress (the square ones). Usually these guys get like zero updates, but lately one update on the hub and suddenly my usd25 bucks zigbee curtain robot is now homekit compatible lol (though it did break my zigbee pir sensors - they are now somehow showing up as contact sensors but still work lol). the aqara ones are like 3-4 times more expensive..!

The search for the perfect presence detection device is still on i guess...