The real problem here is the massive failure (101 W measured) to meet the specified 200 W output in 8 ohms into "70 V" mode. In "Lo Z" mode it should deliver 100 W into 8 ohms, but it also fails at 85 W:
https://www.labgruppen.com/Categories/Labgruppen/Power-Amplifiers/Installed-Sound/E-4:2/p/P0DFD/Specifications#googtrans(en|en)
Well, given the fact that this is NOT meant to be stereo, we may think the 200W Total output power is for both channels cumulated.
I get all that. I just don't get the product's intended application. It's evidently for 'installed' sound. What is that? What kindo of installation? For a thousand dollars?
Well, as the presence of 70V and 100V suggests, it is meant to amplify buildings.
A lot of places have such things: train stations, airports, but also shops, and, in general, any public space, where one need to broadcast (usually) background music and/or messages to public. Can be used for security announcements too.
So reliability is paramount: you never touch it, but you want it to work when needed.
And it's not meant to be a stereo amplifier.
There are 2, 4, 6 channels amps and more.
It's just how you divide the (usually ceiling) loudspeakers load across the channels, for some kind of effective use of the available power.
Or to route different content (messages) to different building area.
This is described somehow in the user manual.
Which doesn't mean this could not be used for stereo. And measuring it is good for curiosity...
Actually, I'm surprised how good it measures
But it looks like there is a push towards getting higher quality sound also for commercial "installed sound".
Or at least to have customers paying more with that goal in mind. As explained in
this marketing content from Yamaha.