Is it true that entrant degree holder at MX 13 gets automatic upgrade to MX12 after one year of service?

Understand that for DXOs in MINDEF, the entry grade for degree holders is at DX9 and they are only promoted if they receive two consecutive min. B' Gradings.

Any reason why MXO people get promoted automatically (if it's true) while DXOs don't? Im asking this as both as considered as civil servants.