Why the Boot Order Would Change When the Boot Drive Is Swapped in UEFI Boot Mode

When you replace a drive that is configured as the boot drive in the front drive bay, the UEFI boot order changes automatically.

This is expected behavior in UEFI Boot Mode. Unlike Legacy Boot Mode, UEFI does not retain boot entries for drives that are no longer physically present.

In UEFI Boot Mode, a boot entry is automatically removed when the associated drive is no longer physically present or accessible. This results in a change to the boot order. When the drive is reinserted or replaced, a new boot entry is created and placed at the end of the boot device list.