Just trying to learn, so hang with me. My speaker manual says how to Bi-amp, and how to Bi-wire both, and my Studio 60's can be Bi-amped according to the manual. I would agree that it would not make any real difference if I was just running a second set of wires. I am pretty sure that when you configure the Denon for Bi-amp, it only sends the low freq stuff out of those speaker terminals.
I guess if you are correct, then it is just a useless function they have built into this receiver.
If the receiver is performing cross-over duty electronically, then you are stacking cross-overs by still having them inside of the speaker. Also, cross-over design by the speaker maker is a little more than a frequency and a slope, so even if the cross-overs were removed from the speakers getting the same voicing by going with an electronic cross-over in the receiver could be a little difficult.
This blurb puts it better than I can:
http://www.audioholics.com/education/fre...ing-vs-biwiring And the linked article at the end goes into waaay more details, and does present come cases where bi-amping works.
It's not a useless feature, it gets adds a bullet-point to the feature list that all the other receiver makers have too. (Where's the sarcastic mark?) Really though, there's truth to that. I think it came about because people were asking for it, and if the receiver is going to get two zones anyway, might at as well add "Bi-Amping" to the list, as it is just a special case of a B-zone. It's like the 300+ Surround Effect Modes that receivers were growing. No real use for them, but since everyone else had that feature...
