What is technical reason that FAN shim does not support Raspberry Pi 3B?

I wonder what is technical reason that FAN shim does not support Raspberry Pi 3B?

It “may” very well work on a Pi 3? If it fits in the case your using and lines up with the SOC. The GPIO pinout is the same on a Pi 3 and Pi 4. Only way to find out is to try it. As near as I can tell nothing bad is going to happen, it will either work or not work.
It was made for the PI 4 and the new Pi 4 Pibow Coupe Case. So keep that in mind. .

EDIT: I just noticed this on the Fan Shim product page
“Compatible with Raspberry Pi 4 (and 3 B+, 3 A+)”

My apologies but the answer does not help much. I have noticed the note “Compatible with Raspberry Pi 4 (and 3 B+, 3 A+)” on the product page and I am trying to understand why it is not compatible with Raspberry Pi 3B (3B has the same pinout, the same SOC line up etc. as 3B+).

I would say if it works on a 3B+ it will (should) work on a 3B.

I get a confirmation from the re-seller that it will work on 3B but “some features” will not be accessible.
I still do not know what functions will not be accessible ;).

Based on the feedback from the re-seller LED will not work, FAN will not adjust to the temperature. It is interesting if this is purely SW issue (https://github.com/pimoroni/fanshim-python) which could be adjusted for 3B?

I’d run the installer anyway and see for myself what works and doesn’t work.