Adrien, my thought is that turning the sub down, or more precisely, leaving it at a properly calibrated and balanced level rather than setting it "hot", does result in less "flabby" bass. The reason being that the very low bass notes handled by the sub are neither "tight", "quick" or "musical" in themselves. Those qualities in bass instruments result from the harmonics which are handled by the speakers, not the sub. Playing the sub at too loud a level with respect to the speakers results in the "flabby" fundamental being unnaturally prominent compared to the "musical" harmonics.
As has been suggested before, it's interesting to listen to what comes out of a sub with the usual receiver crossover setting of 80Hz or lower remaining in effect, but with the speakers simply disconnected so that what's heard is almost entirely the fundamentals in a bass-heavy passage.
