I think all futaba flight packs are packaged with R127DF receivers. That receiver definitely has high/low bands. (I just purchased a Futaba flight pack.)

Based on my incomplete understanding it has something to do with the dual conversion processing. I find this to be a good article about dual conversion:

http://www.torreypinesgulls.org/Radios.htm

I believe the high/low band distinction has to do with the tuning of the second stage of the dual conversion decoder (i.e. the one that operates at 10 MHz in the article above). Perhaps futaba have two slightly different intermediate frequencies, one low band and one high band.

It would be interesting to find out exacty what technical considerations have led Futaba to split the receiver bands.

... shame the hobby shop fed you the wrong info.