Things are a little more complex than how you present them. For example, multichannel absolutely does not imply that you are among musicians as you describe.
And even all the channels can be front-facing : the recordings made on front channels are quite remarkable : the precision of the soundstage is greater than with only two channels.
The recording can add to these three channels two rear channels broadcasting the ambient sound which returns from the room itself after bouncing off the walls. Classical music lovers who go to concerts experience this with great pleasure... even when they are in the first rows which are never the best in a room when you listen to an orchestra... The best seats are rather front in the second half of the room: where the direct sound and the reflected sound are balanced. Numerous recordings of orchestra and even solo instruments published on SACD, audio or video BD demonstrate this. Even a solo cello or a solo piano gain in realism because the precision of the frontal scene seems even more precise.
You are correct. This is true if that is the way the music was recorded. Correct me if I'm wrong, but this would apply if the recording was made live with mics. But would not apply to a studio recording? And I suppose I would be less likely to have ambient information if recorded, say, at the Hollywood Bowl, the Greek Theater, or an outdoor concert, but would be more likely to have it if recorded at an indoor venue. And would probably be especially enjoyable (if recorded for this purpose of capturing the information) if recorded at a well-designed hall such as Boston