That is correct. The sub is a dumb device and can only switch itself on from standby mode. It won't auto-choose it's own EQ profile: it's the receiver which decides to output a LFE signal to the sub, depending on the input signal channels and/or the surround mode you put it in.
If you select a 2 channel source and the receiver is in stereo or "pure direct" mode (or something similar), your subwoofer will not receive a signal. There is a possibility to get your sub pumping in stereo mode: set your fronts to small in the receiver settings. Your first question was about the crossover setting, so I assume your fronts are already set to small. The crossover has no job if the fronts are set to Large, cause there is nothing to cross (Large=fullrange) So set and keep them to Small, crossover to 60 or 80 Hz, depending to what sounds best and.. enjoy