I doubt that actual hardcore Scrabble players would care, any more than a hardcore chess player would mind if you kept referring to an index card with a diagram

I doubt that actual hardcore Scrabble players would care, any more than a hardcore chess player would mind if you kept referring to an index card with a diagram to remind you which way the horsey moves. Of course, they would care about you having access to the entire dictionary, just as a serious chess player would object to you having a collection of chess opening or endgame reference books to hand. At a beginner level, it's more fun when no one knows the word list perfectly, and you shouldn't allow it. At a slightly-above-beginner level, say where one player knows the two-letter words and others do not, knowing the two-letter words is such a huge advantage that it's a sensible house rule to level the playing field a little, and likely make it more fun for both.