I'd never heard of this before. One of my former managers is really into Home Assistant and has done a lot with his setup, but I think all of his motion detection was IR. How's your 'radar' setup? Do you get a lot of false positives/negatives? How's the distance on its detection?
Something like this https://i.ebayimg.com/images/g/nvAAAOSwEK5fmkrH/s-l1600.jpg
No I'm not, but those work too.
This is what I bought: https://www.ebay.com/itm/153285261299
It is described as a radar sensor because it uses a high frequency oscillator and monitors the change in the signal due to things moving in the electromagnetic field. Imagine the effect of waving your hand near the aerial of a radio receiver when the signal is weak.
Until you're drunk AF and trying to take a piss (or whatever it is you're doing) at 1am and then the "smart" light blinds you.
Here's my solution: https://www.ebay.com/itm/265164805260
It's very convenient to have the light come on automatically in stairwells and lavatories. But you are right about it taking much longer to pay back. My calculation is that compared to having the LED bulb on continuously it pays back in about two years.
I have several infra red motion detector bulbs in stair wells and in the pantry as well as 'radar' bulbs in several other places (these detect movement by the disturbance in a low level high frequency radio signal).