Which is what they also say on the link I posted. Quite a few think he wasn't given enough of a chance under Sven, but keep it vague, whereas a few actually mention specifically that he isn't geared towards a passing system.
I saw on a forum that Waghorn was good under Pearson because they could knock the ball over the top for him to run onto, but lost his way under Sousa and Sven as they like teams to play a bit and he doesn't have the control...