The transverse crest is found on non Spartian pictures too, it is very rare anyway.
There is for example a coin from Messembria in Thrace showing a Corinthian helmet with transverse crest. Is it an officer's distinction? Most authors today say yes. But we have no ancient proof for that.
I would use only one per unit for that reason and other towns surely used other styles do denote an officer. Athen 3 feathers?

