"It's amazing that he's played rugby all his life but he doesn't know where his head's supposed to go when he plays seven," Youngs said.
"That's Jonny for you. Scrummaging's not his forte but give him the ball on the edge of the pitch and he'll finish for you.
"Mako was a little bit confused when he saw Jonny's head pop between his legs. God knows. Luckily we got the ball in and out."
England fullback Mike Brown questioned the choice to put May into the set-piece fray.
"He couldn't have watched much rugby or scrums in a rugby game to bind the way he was binding," Brown said.
"That's just Jonny. Interesting technique, I don't think it'll be one that they'll be using going forward, but it made us laugh.
"I want to know who put him on the scrum. That's a good question, who actually put him on in the scrum in the first place? Because he'd be the last person I'd [use]. That's who needs to answer some questions."