Most high-quality loudspeakers are 4-Ohms

....no....

It is true that high quality speakers are more likely to be lower impedance than they were 40 years ago because single driver systems, Lowther, Tannoy etc are no longer dominant. Multi driver speakers are more likely to be lower in impedance. But impedance alone is not indicative of quality high or low.

Nope. But you knew that, didn't you :)?

Stan said it well.

Count all the two ways, or book shelfs and the figures get more in line to higher impedances.