I agree with this, I also think the orientation of the valves makes a difference. Mopar SBs have the same valve angle (23*???) as the "racing" Chevy wedge V8s and they also open on the center of the cylinder; I believe this is what gives Mopar engines that extra "crackle" which makes them sound more intense than comparable Ford/Chevy engines. And Mopar BBs have really long connecting rods compared to the others so the piston dwell time is pretty long; this gives them the extra deep "chunky" sound at lower speed.
IMO I'd have to disagree with the Hemi sound, I think they do sound noticeably different from wedge engines when the RPMs are brought up. Both new and old Hemi engines get much louder and make a deep BOOM-BOOM-BOOM sound when the revs start to climb whereas a wedge engine stays more constant in tone throughout the rev range. I feel like this is due to the increased breathing efficiency at higher speed but it could all be in my head LOL