If the goal is to get surround sound, then you are correct, but if the goal is simply to use a pair of speakers you have laying around for full range rear fill, then you CAN connect them to the front B connections. The fact that he is wanting them to work with 2.1 content tells me that he's not...
What connections do you have the front and rear speakers connected to? If you notice on the front of the receiver there are two buttons labeled "Speakers A and B" If your goal is to have stereo surround, you can connect one set of speakers to the "Front A" connections and the other set to the...