That's not exactly correct. The 1070 and 970 can have a digital audio input assigned to the front video input, but that's as far as it goes. The 990 takes this one step farther, as it can have any digital audio input, component video input, or DVI video input assigned to it. If you have a source that uses composite video, s-video, or analog audio, it would need to use one of the rear panel inputs.
I used this ability with a couple different video sources during the years that I had the 990 (especially when I had an HDMI switch upstream of the 990's DVI switching) since if it used a digital audio connection and any sort of HD video connection I could use the front input for it. Sources like the SMS-1 and Wii had to go to a rear panel input, but something like a DVD or HD-DVD player could use the front input and thus help free up a rear panel analog input.