Maybe it was a mistake at the mastering stage when exporting LFE channel. I can't think of any reason that would have been done. 80hz and below are extremely important for classical. I used to know a guy in school who had giant subwoofers in his car and liked to play classical music. He would pull up to a stoplight with Beethoven rattling his license plate. Crossover point is a balance, too low and you are wasting the efficiency of the mains and possibly creating room mode conflicts, too high and you are getting directional bass from the sub. Crossover point is also not a sheer cliff, so a crossover of 100hz will bleed well into upper bass/low mids and you will start to hear the mumble of male voices in your sub. I've found an 80hz crossover works best for me.