ACPI debug via COM port stops after Windows 11 loads

I enabled ACPI debug output to the serial port in the BIOS, and it works very well during boot.
The output of ADBG() in the ACPI tables are visible on COM3.

But the ACPI debug output on COM3 stops when Windows 11 has finished booting.
If I read the memory at the ACPI memory buffer address listed in the BIOS, I can see that ACPI debug is still being written after boot, but output via the COM port stops.

Reading from memory is OK for getting the debug output while the OS is active, but I would like to see the debug output while the OS is shutting down. Once the OS has booted up, the memory space is cleared, so the debug output sent while shutting down is erased.

Is there a way to keep the ACPI debug output via the COM port working after Windows 11 has loaded?