Yes. It's PU as well as training wheel.
So we know Zoro has the ability to cut cliffs and such so it didnt boost his power and even if it did it would go against being a swordsman.
Not if that cliff is bare minimum(Demo) and Enma allows Zoro to do much better than he did in DR.
And for that All he needs to do is use his strongest attack and unleash Enma to use majority of his Haki in the slash.
Being able to tame is required to not get knocked unconscious running out of juice, or waste Haki unnecessarily in attacks. If he had to cut Kaidou i bet he could have done it without training but it would have been hit/miss case, a one shot with Zoro ending up being unconscious.
Hence it is a PU with a drawback for which Zoro needed to train to use it effectively.
Zoro said Enma's Power
Now this is just laughable. A told by kitetsu a master swordsmith Enma has no power of it's own it takes a lot of the wielders ryou so all enmas power is zoros power
Luffy 1st PU this arc is learning to out his Haki i.e Ryou. Just that.
So even if Enma uses Zoro Haki, it helps him out more Haki than he originally could. Hence a PU.
As for why i consider it training wheel, the more better his control over Enma to keep it restrained from using his Haki, the better his control on Haki will be. So in the longer run his control over Haki is also getting substantially faster better.
Peace out.