Nothing wrong with getting a bit of time in a CSU single retract.
Too often today the first CSU retract that some pilots fly is a twin, which flies a third as fast again as anything they've ever flown.
A twin is a pretty big step up from what they've been flying, getting used to setting MP and RPM including getting the props in sync, raising and lowering the gear while climbing faster and having a significant increase in speed isn't necessarily a simple exercise.
Getting experience in a CSU, retract single prior to flying a twin has some value IMO.