Yes. "never" is a strong word here. Assume when he says "never" he means, "EY thinks it is really unlikely for K to do".

Yes, the sane meaning for “never” is ‘negligibly often’... but then again the sane meaning for “sometimes” is ‘non-negligibly often’.

In other words, when EY sees EY-playing-K-but-Selecting-Moves-Randomly-in-proportion-with-predictions-of-K, and observes RYK has played an unexpected/unlikely move, EY concludes that RYK has probably picked a move that is evaluated to be less fit than some other move. RYK is a worse player than EY because RYK is not picking its best options. RYK is the gambler that sometimes takes the sucker bet.

I do get his point, but I think that sentence in particular is paradoxical. Had he said “rarely” and “rarely” it'd be OK, but “sometimes” and “never”...