Nonsense.
How is there any evidence of anything different?
Well, if we want to nitpick, there's 3 Premier League goals in 5 starts in 2009.
The line between success and failure for forwards is thinner than for the others 9 players on the field. We've seen it with a lot of strikers, upset the balance of their reponsibilities and their return drastically changes. Look at Leon Best; as the main man he couldn't stop scoring.