“Works with Sonos” wouldn’t have anything to do with audio sync. Anything coming from the Sonos to the receiver would be in sync with the receiver’s speakers, anything going from the receiver to the Sonos would have a slight delay, variable depending on what input and settings your using.

I mean the ability to play what I’m sending to my Sonos system (in this case, Spotify from the Spotify app or the Sonos app, I don’t really care which) playing out of the Port, which is connected to my receiver, to play audio in sync/without echo, with all the other Sonos speakers, so basically delaying all the other Sonos speakers by a few ms to account of the processing that goes on in the receiver, which is important since many modern HT speakers expect a subwoofer to provide most of the bass, and also to provide room correction.

If you’re playing “to” the Sonos system, then both your Sonos system speakers and the speakers on the receiver will be in sync.

Assuming that there’s no delay on the signal after going in to the receiver. That’s not under the control of Sonos. Most receivers have a “pass through” setting for this kind of thing. You might be able to check with the manual for the Pioneer to see if they do any delay/additional processing of the signal.

Unfortunately that’s not the case. My receiver, like most receivers (a quick search of this forum shows this has been a problem with Sonos setup for years), add a bit of delay for audio processing. I can use the “pure direct” mode, but as I mention above, this bypasses using a subwoofer and room correction, which are important to sound quality. This seems to be the case with most receivers, I’ve see some posts on forums say that the Pioneer “Works With Sonos” receiver fixes this, but I’m trying to get a bit more clarity on that, especially since the people who have posted that “Works With Sonos” were using Sonos Connect, not Sonos Port, which you would expect as the Port, as the Connect’s successor, would be as good, if not better, at this, but I’ve found too often things like this are overlooked.

Also, quite to my frustration, I had no problems doing this for years with my Denon 3808Ci and AppleTV, and multiple zones of AirPlay v1, but since moving to a 4K/HDR receiver, it’s been a big challenge. Ironic since my phone is now faster that the computer I used when I was first able to do this, but audio processing latency seems to have gone up with receivers over the years.