That's because MS "officialy" supports the installation on computers that comply with some of the requirements (ie TPM 1.2) but with disclaimers. You just have to check some acknowledgement checks before the instalation starts.
I had a different experience on the 3 unsupported computers I upgraded:
- My daughter's laptop (7th gen, 16GB RAM, TPM 1.2) -> update from Win10 to Win11 with disclaimers using unmodified ISO.
- My old Surface Pro 3 (4th gen, 8GB RAM, TPM 1.2) -> clean install with disclaimers using unmodified ISO.
- My wife's X99 desktop (5th gen, 32GB RAM, NO TPM) -> had to modifiy the installer to be able to do an in-place upgrade from Win10 to Win11 with disclaimers.
My other computers: Surface Pro 6 (8th gen, 8GB RAM, TPM 2.0), son's laptop (8th gen, 16GB RAM, TPM 2.0) and my main desktop (9th gen, 32GB RAM, TPM 2.0) upgraded directly from Windows Update
Interesting....the Optiplex 3020 I tested didn't give me any disclaimers (which I know is not officially supported with the 4th gen i5).