as a person who thoroughly distrusts manufacturers' specs, gotta ask, any idea what any of the deviations mean, as a practical matter? Do you believe, for example, that if my source material's power distribution is pink-noise-like - so equal power in each octave, that the third octave where the speakers' impedance is lowest defines the impedance the amp sees? Or is reality more your cuppa? Any idea how that third octave of lower impedance affects the amps' linearity or distortion? Or is the sky just falling in general?
I don't have a thorough mistrust of manufacturers specs, but rather I do realize that they are often a bit "fluffed" as a means to sell more product. It's the world we live in (and it's round, if you're keeping track). Does my ford Focus actually make 160hp? I'm sure, at the crank, you could find the right combination of fuel, altitude, ambient air temperature, cooling system temperature and oil temperature/viscosity to have that be true. But will it's power rating always be 160hp, or will it infrequently be 160hp, based on all those things? Furthermore, how much of that 160hp is actually useable, not robbed by the transmnission....will I always be driving at the 5000rpm needed to be in the max power band? Lets say that I actually use between 50 and 100hp during my daily drive. Doesn't sound as impressive as 160, does it.
The way speakers are specd are not dissimilar to that. It is a device which presents varying resistance to an amplifier based mostly on content (as you pointed out), but also on cable capacitance and manufacturing tolerances. A more accurate representation of a speakers impedance would be stated as a range, based on the frequency range of the speaker. "Nominal" is a fictitious number based on my speaker running at 5000rpm, downhill, with a 50 degree Fahrenheit gale force tailwind.
