Sounds like it does the same thing, just need to activate it differently? Maybe something that happened when Pioneer/Onkyo merged?
No, it's NOT the same thing. IntelliVolume allowed you to set a certain input source's preamp sound output level via a range from -12dB to +12dB, almost like an old power amp's sensitivity control. My Input Volume acts like a starting volume setting for each input -- so if you want, say, the CD input to always come on at "25" on the volume, this is where you set it.
This MAY have happened when the companies merged, because it was around that time that things changed in Onkyo's AVRs, if my memory is correct. All I know is that the feature has been gone for a few generations now. It was a big selling point for me in an AVR, as it allowed me to do what you don't care for -- achieve a louder level at a lower volume number. Denon still offers a feature like this, and they call it Source Level or something like that; it was one of the reasons I picked up a Denon when it came time to switch out the Onk.