Question on Speaker Placement

The only thing that matters is how it sounds to you.  From your description you will likely get more lower frequency SPL from the speaker in front of the wall while the speaker that is floating won't be able to match the others SPL.  The only way to really discover what they're doing is measure the speaker's responses.  The free REW software is a great tool to sort out difficult rooms.  Keep in mind that when speakers get more than 9ft apart it gets more and more difficult to get good imaging.  Good luck and cheers. 

Many years ago John Rutan at Audio Connections in Verona, NJ had a listening room configured with the speakers along a diagonal of the room, rather than parallel to a wall. It sounded great with all the speakers I heard, probably four pair. For the past couple of years, I’ve finally had a room that’s amenable to such a setup, and it works out really well. Now, I’m using dipole speakers, but none of the speakers John played for me were dipoles, and they all sounded good in that configuration, so it’s probably worth a try if you have an appropriate room. And using a real time analyzer app, I seem to be getting pretty flat response, although I can’t compare it to the response in prior rooms with parallel configurations because I only discovered app after moving to my present house. 

Find a track you really  like that has full dynamic range. Place tape on the floor where your speakers are.

Move them all around, each time listen to that song. Place tape where you think things work, repeat till you find the "sweet spot"

When you figure out what sounds best, leave the speakers there. 

I recently listened to a person's system that looks like it would sound terrible.  One speaker close against a glass side wall and the other sidewall open to the room as you describe.  It sounded glorious.

So sometimes the rules are not as written in stone, although I agree there was luck involved with excellent system building. 

Just got to try it.