Yes, that's expected, you need to rebuild the disk to fix that, but first check the lost+found folder, if there are lots of files there and/or the emulated disk is missing some data you should not rebuild on top of the old disk, you have more than one option:
-rebuild to a new disk if available, then you can compare the data with the old disk
-compare the old disk with the emulated disk now, you can do that by first stopping the array, unassign disk3, start the array, Unraid will continue to emulate the disk, use the UD plugin to mount the old disk and compare the data with the emulated one, just note that before mounting the disk with UD you need to change the XFS UUID since it will be the same as the emulated disk, you can to that in the UD settings
-final option is instead of rebuilding the disk doing a new config (Tools -> New config) to reset the array and re-sync parity based on the actual disk3, which should not have the lost+found folder but you should confirm before doing it, using the same procedure to mount it with UD as described above.