Hi Bill!
That's what I'm getting at. It's where you are putting the Speakers in relation to what Dolby is spec'ing for placement. And it is all about the angles.
I think if he left those Side Heights where they were after moving the couch, they should be called Top Back in the AVR.
This is much the way my installation will be progressing, with "Height" wall mounted Speakers being used in the most proper locations to call them Top Front and Top Back. When I was measuring everything out, I had to struggle with whether mounting them as Front/Rear Height would be smarter because I can more easily nail those angles. However, the Tops Front/Back placements are routinely suggested to give more joy.
In my situation, the Top Back is slightly off Spec, but close enough that I'm not too worried about it. I base that on my experience with the Rears having been effectively at Rear Height placement before bringing them down to floor level.
Anyway, Even trying to create a hybrid Auro effect, sending Rear placement info to the sides of the seating is ineffective. Of course, Auro in the US is mostly a dead thing except for the resurgence now of Auromatic upmixer and such... but most all programming is encoded with Dolby's spatial queues. So at best, he would be better off mimicking a hybrid placement of the Tops as Side Heights.
If the AVR is forcing him into only using Height or Top Speakers, then he should choose what he can make work best in the room, recognizing that the placements matter a lot in this type of setup.
In the end, as I said, it is his room; his system.
Advice is given. Horse is led to water.
Get the right information sent to the right place. If placements are hybrid to achieve both specifications in some way or another, cool. But it has to still be done smartly and with more intention to hope to get the effect he wants.