It looks like the upgrade partition is not transferred successfully to the boot partition after the reboot.
Have you tried to hard reboot it or reboot/shutdown from the VM host instead from WSA? if you have not, give that a try and double check again after the WSAv comes up to see still reflecting the old version.
If its still showing old version, recommend to contact TAC and open a case since looks like there is corruption somewhere in the OS level.