That's a really good question. It's likely his mental processor. You know the old "he can't walk and chew gum at the same time" insult? That's probably the case here. His foot churn was probably carrying him out of plays and causing its own issues, so as a pro, they're probably asking him to calm down...and with him, it's probably interpreted as quieting his feet.(Funny enough, his brother Mathieu...is all foot churn and wide speed and little else - but as a winger, it has a place in the NHL).
Really, you'd like for a player whose best asset is skating (to be on another team, if I'm GM) to have the mental processor and anticipation ability to either J-cut up and/or surf to disrupt or absorb rushes more efficiently. Joseph isn't confident or competent enough to do that...so his process is: eat, recover...eat, recover...eat, recover...it's the defenseman equivalent of "puke and rally"...
Unfortunately, I don't have infinite time to find instances where P.U. gets beat wide...but here's an example of his process of eat/recover.
You can watch the video here, you can see my video timing in the following screen caps...
Dylan Larkin has the puck off of a sudden-ish change situation in the NZ. It's tough to absorb these sometimes, but this one starts deep in the gutter. So, it shouldn't be hard to diffuse this given the situation. He has partner support, he has back pressure, and the lead rush is the initial puck carrier...this shouldn't be a good play for Detroit, this shouldn't turn into any sort of rush chance. Let's see...
Hooray! P.O. is gonna shut this **** right down. I always told my players, "plays that start in the gutter, die in the gutter". What the hell is DET71 gonna do here. He's a whole zone ahead of his linemates. P.O. has slid to close him off. This can be a stick led close off and should force a dump in. His defense partner can be ready to pivot and retrieve this freely because he doesn't have to babysit the line...plus he has good back pressure/support from his forwards. This should end up as a quick turnabout for the Penguins. Can't wait...close'em off 7-3!
Oh...I guess "recover" time had ended and "eat" time has resumed. Joseph cannot process what's happening fast enough and is scared off by...I don't know...realizing that it's Dylan Larkin...or the speed, for some reason...or just trying to over-correct for mistakes that he was making in junior and misread the pattern recognition of all this. So, somehow he back skates away from the puck carrier. Look around...he cannot pass the puck to anyone and still be legal. But P.U. is determined to let this play fester...but there's another "recover" scenario coming, let's see what he comes up with...
"I know! I'll just..."
"Oh, pour s*** right into my c*** you f***!" That's the inner monologue of P.U. as he somehow allows the middle of the ice, allows a clean zone entry, and is going to create a rush chance off of
that piece of garbage entry. I think this ends up in the net because of bad goaltending...but this wouldn't need tending if P.U. had an M.O. towards being P.O.