So Imu was indeed a third form and even ackwoledged Loki's strenght (same guy that in first form was upset over how weak Luffy was btw).
Real issue is Oda off-screening Loki vs Imu's second form, if we got one or two chapters of this fight beforehand I would have no complaint, kind how weird to tease hybrid Loki for so long and not doing anything about it, but maybe he's getting up for a team up with Monkey King.