Yes, it can work on some occasions, but just because it didn't hinder Henry out left doesn't mean that every single forward who is shifted out wide is going to benefit from it.
That's like saying if a player takes longer than usual to reach his prime and doesn't play well until he's 27 say, that every single player who hasn't lived up to his potential at a younger age will when he reaches 27.
It may be true in some cases, but some players will be hindered if they're shifted out of position for too long. Thankfully though, Welbeck has a lot of attributes that help him out wide so I doubt that it's going to be the case with him, but just because it benefited Henry in the long run doesn't mean it's guaranteed to benefit Welbeck. That sort of logic is utterly ridiculous.