It's true that the effect of the filtering is practically inaudible, if the sample is played at the rate that it was encoded at. But in MODs, the samples can be played at all sorts of rates, which can make the effect of the filtering very noticeable.
While testing, I found that the filtering made some samples sound "dead", and using "-k" brought them back to life. There probably are some tracks that'll sound better with the filter, but I didn't find any