No, the LFE doesn't have anything to do with it. Setting a xover frequency for the LFE is a useless feature IMO. The LFE can be as high as 120 Hz but is usually much lower - if you set the LFE to 80 Hz you will effectively discard all the frequencies greater than 80 Hz for those few soundtracks that have LFE content greater than 80 Hz. Very few receivers lets you set that and for good reason.
How much is routed to the surround back speakers is dependent on the mix of the soundtrack you are playing. Some will have a lot of content there and some will not. If you use a matrix decoder like PLIIx you may get more sound from the surround backs as it will synthesize those channels from the original 5.1 DD-EX.