“RACK MANAGEMENT”. The letters which are good for making bingo words are also useful in making words when you have a bad draw. The millions of computer simulations of games have shown that “bad draws happen more frequently than previously assumed”. (I could have told them that from my own experiences). So a separate advantage of a 5 letter word over a 6 letter word is that the draw to replace the additional letter carries the risk of a bad draw. As part of the emphasis on defense, Nigerians have also compiled a list of 5 letter words that are awkward for an opponent to play off of (and competitive Scrabble is all about memorizing lists).
All of these defensive strategies go under the name of “rack management”.