This is happening with both my Z690 Extreme boards as well, on any BIOS. First board was bought in December 2021, the second board in March 2022.
Sometimes they will stay at Qcode A0 and sometimes at 00. Everything works perfect I've had zero problems with either system. One of them was given away, the March build is my current day to day system. The code also changes from A0 to 00 or the other way around when I reboot the system, say after a Windows update.
I have fast startup/hybrid boot disabled in Windows 11 (powercfg /h off) but left fastboot enabled in BIOS.
I can't see any difference in system behaviour whatsoever, all devices are working, PCIe link speeds etc. are identical, performance is the same.
No idea whats causing the board to jump between different Qcodes. I saw a few other users reported this months ago on overclock.net forums.
Since everything works fine I chose to ignore it but I'm still curious whats going on here.