Well, the bitterness in the beer I make comes almost exclusively from Hops, not salt. (There are a few other possibilities - some good, most BAD, like tannin extraction from grain hulls which leads to astringency)
Hops impart bitterness by way of their alpha acid content, which is isomerized during boiling... (God, I sound WAY too geeky....)
Having not seen the show, maybe they were talking about some sort of checmical reactions on the taste buds or something??