I ran out and grabbed a Sonos AMP so I could test this out myself since I have some upcoming installs where I had this spec'd. I connected a pair of Sonance VP86R's that I had for an upcoming job.

I did some quick testing with Apple Music.

When you first install it asks you what type of setup this is:
1) Stereo Speakers
2) Front speakers connected to TV
3) Surrounds.

Says this can be changed later but.... unless I am blind there is not way to change this. Thus, software issue #1.

I choose stereo speakers and imagine so did Brendon and Golden. Now I was in my basement and not large. The AMP volume is low until you hit about 75% then it ramps up and was pretty damn loud at full volume. However, it did feel lacking, especially in the bass dept. I checked the volume limit and like others was on 100%. I brought it down to like 10% went out of settings screen and then back to 100% just to make sure no software issue. I then went into EQ and cranked up the bass but only had a marginal effect. Loudness toggle also didn't seem to make a difference. Now... I did see in advance settings there are settings for the sub. This is set to ON, which I thought was strange. So thought maybe this had an effect. I tried toggling off, then on and no real difference. I tried changing the crossover so that way more bass would go to the speakers and not much difference. Think this is software issue #2 and will call Sonos tomorrow. Thought maybe its just cause these are in-ceiling speakers and not installed so somewhat lackluster.

As I said there was no way I saw to change modes (speakers, TV front speakers or surrounds) so I reset the AMP back to factory settings.

Now the weird thing was the room was still showing in the Sonos app for a while even though I closed the app and re-opened a few times after the reset.

Went back through setup and this time I picked the front speakers connected to a TV option. Under this setup it asks if you are adding a sub and I selected no. Same with surrounds. Skipped most of the TV setup and then tried same songs. Now I had Bass and it sounded much better. I went back into room settings and saw EQ settings were still in middle with loudness on. Went to advance settings and into the sub and saw it was still selected ON but had the crossover set all the way down to 50HZ. Previously, with stereo speakers, was in the middle but had no effect.
I'm assuming this is what Paul choose in his setup and may be why his sounds good.

For the others who had issues, I am curious if you reset the AMP back to factory default (unplug and while holding down the sync button on the back plug the power back in and keep held down till its blinking green) and then choose front speakers for TV and see if that makes a difference in the sound.

Will test more tomorrow and try connecting to TV via HDMI to see what that sounds like.