I am also experiencing this on Unraid 6.12.3. Running inotifywait shows hundreds of access events over a few seconds for /boot/bzfirmware, and this applies to other files under the /boot directory as well:
$ inotifywait --timefmt %c --format '%T %_e %w %f' -m /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
Sat Sep 30 21:17:43 2023 ACCESS /boot/bzfirmware
For me this is actually causing other applications to hang, as the CPU utilization caps out due to the amount of iowait on the system.
I use Netdata and have attached screenshots showing the CPU util (note the iowait) as well as the i/o for sda, which is my boot USB.