The Onkyo and Pioneer receivers you're discussing have substantial and similar 4 ohm capability despite the lack of the 4 ohm rating.
I don't see how you arrive at that conclusion. As you say, the SC-1522 and Onkyo 3008 are neither given FTC ratings at 4 ohms, but Pioneer does give continuous power ratings for 9 channels at 4 ohms for the SC-1522 while Onkyo does not give such ratings for the 3008. That's a fact.
You appear to be paying far too much attention to speaker impedance ratings as they relate to amplifier requirements.
Maybe the impedance ratings are unimportant, but that was the subject of discussion, wasn't it?
