It could be because 152 is going to ESF and are less ready to take on modern DDGs than SSF (which is why 172 entered service quicker).
Or, maybe entering service doesn't mean very much in terms of combat readiness, and 152 might not yet be commissioned but may be mor combat ready, than say 172 even though the latter is commissioned.
Or, maybe entering service doesn't mean very much in terms of combat readiness, and 152 might not yet be commissioned but may be mor combat ready, than say 172 even though the latter is commissioned.