In that amp in the Harbeth video, it is showing apparent power over a synth pedal tone that is right at the phase minimum of the speaker. Further discussion here:Compared to this video, what to believe?
I'm kinda more inclined to believe the chap that is using a multimeter because that is showing real time voltage values, surely those power amps are just showing the power usage which would make sense for a power amp of that size, a massive power amp is going to consume a lot of power, if you had a 50w power amp with a wattage metre slapped on the front it would scale accordingly.

How important is doubling down power to 2 ohm or 1ohm on Hi Fi Speakers on high dynamic range music?
From the impedance plot, the magnitude of the impedance at 50 Hz is magnitude about 20 ohms. That means that not a lot of current is required. The fact that there is a phase shift of about -50 degrees at 50 Hz just means that there will be a phase difference between the voltage output and the...

Tldr, I think it’s misleading.