Spoofless sounds really cool.With 0.3.2 spoofless SMBIOS and SIP enabled, there is no OTA delta to 11.6.2 and the full installer will not work complaining of needed firmware update. Build with minimal SMBIOS spoofing, all works perfectly.
I am using 0.2.4 at the moment (not going to Monterey), but maybe I will try out new release 0.3.2 on my mini.
Probably want SIP and secure boot on.
Let's see if I encounter same problem as you with no OTA delta to 11.6.2.