Wild shape as a bonus action usually offers the better tactical advantage over wild shaping as an action, however sometimes it’s better as an action. You may want to shove that enemy over ledge and then wild shape to stand up against enemies, or maybe you have an item that grants misty step you want to position your wild form as tank.
It feels a bit wrong that a land druid can pull off this kind of combo while a moon druid can’t,
even if it’s not RAWApparently this is the proper ruling, as demonstrated in this
sage advice.