It means that Microsoft won't suddenly disable your Windows 11 install's ability to update. Microsoft has already, on at least one occasion, disabled further updates for computers that don't meet their specified requirements in regards to processor and TPM.

A lot of the users of 10 we're talking about wouldn't know how to get Windows 11 working again after updates were stripped again.

If there is no tpm then it’s not secure I assume is what is meant by not “fully supported.” You can do it, but it’s on you if you get bootkitty.