I can't imagine why you would have to do that. Regardless of where the fermentable sugars come from (as in from table sugar, from your malted grains, candi sugar rocks or syrup, etc.), that yeast should be able to handle it.
So I would say, no that's not specifically necessary. Mind telling where you read that?
Also, not telling you how to brew since doing things your way is the best part of brewing, but I personally wouldn't make an American IPA with that English ale strain. I would make an English style IPA or Brown ale. But that's me.