" Enveloping soundstage vs. speakers close to wall behind them=pretty much mutually exclusive."
"Pretty much" yes, but perhaps not quite entirely, "mutually exclusive". So I agree with you.
Acoustician David Griesinger was speaking about good seats in good concert halls when he wrote the following about "envelopment", and imo it’s useful, relevant information:
"Envelopment is perceived when the ear and brain can detect TWO separate streams: A foreground stream of direct sound, and a background stream of reverberation. Both streams must be present if sound is perceived as enveloping."
Implicit is a time delay in between the arrival of the direct sound and the strong onset of reverberation. Obviously this time delay will be different in a home audio setting than in a concert hall, but ime the general principle is still applicable.
When designing a listening space, acousticians will typically work to manage reflections such that early reflections are minimized, but without eliminating the reverberant energy which arrives somewhat later. In other words, acousticians are into this time delay separating the direct from reverberant energy, showing that it applies to small rooms as well as concert halls.
When the criteria for envelopment are met in a home listening environment - "a foreground stream of direct sound, and a background stream of reverberation" - we can enjoy both clarity AND envelopment (assuming there are no other significant problems). When there is insufficient time delay between the direct sound and the strong onset of reflections, clarity is degraded and envelopment doesn’t happen. This is why dipole owners like to pull their speakers well out into the room - the path length for the backwave imposes sufficient time delay before its arrival at the listening area.
Now there are of course major differences between the acoustic signature of a space where music is created (like a concert hall) and one where music is re-created (a home listening room). In our home listening rooms, in effect there is a competition between the spaciousness of the acoustic signature on the recording (whether it be real or engineered), and the inherent "small room signature" of the room we’re playing back that recording in. The ear will select whichever combination of cues seem the most plausible, and all too often the "small room signature" is dominant, especially when the speakers are quite close to the wall behind them. The ear can usually sense the presence of that wall.
But it is the earliest reflections which most strongly convey undesirable "small room signature". If we can minimize those early reflections while preserving the later ones through a combination of radiation pattern control and aiming those radiation patterns intelligently, we can tip the scales in favor of the acoustic signature of the recording venue. Then ear is able to pick out the decaying reverberation of the recording venue from the in-room reflections, without the playback room’s signature dominating.
In other words imo it is possible to have enveloping soundstage AND speakers close to the wall behind them at the same time, though doing so falls into the category of "things easier said than done". I think I know how to do it, but thus far not without rectangles.