Basically, Lin felt that William Daniels, who originated the role of John Adams in 1776. was so iconic that everyone will just picture William Daniels' version of the character and know exactly what they're talking about.
He was obnoxious and disliked, we know that sir.
Amittedly, I'm in Massachusetts. We have a soft spot in our hearts for our loudmouth lawmakers. None of them perfect, but there's a bit of a tradition, starting with Adams.