This is expected behavior.
To retain the preferred hard disk order when adding or modifying the SCSI address of the virtual hard disks:
- Power down the virtual machine.
- Log in to the VMware vSphere Web Client.
- Right-click on the virtual machine from the inventory and select Edit Settings...
- Remove all hard disks from the virtual machine while retaining the virtual machine disk files.
- Add each hard disk in the desired order while selecting the preferred SCSI address.
- Click OK to save the changes to the virtual machine configuration file.
Note: While creating a VM, use EFI instead of legacy BIOS. If the VM is already created with BIOS. If possible recreate a VMX with EFI.