It's usually not anywhere near that complicated. To use an example from the article he folded a QJ against a QT with 89J on the board with no flush possibilities. In this case there are not very many hands that can be beating him: the pocket pairs AA, KK, QQ, JJ, 99, 88, stuff that makes two pair like J9, J8, 98, and the straights QT and T7. Overall this is going to be close to the chance when holding 77 that your opponent has a higher pair, which most professional players will "just know" is about 3-4% because they memorize tables of such facts[1]. This means he should believe he's a pretty substantial favorite and why the fold was so unexpected.

[1] https://poker.stackexchange.com/questions/1203/pocket-pair-s...