I'd say the short answer is "yes."
As the first photo indicates, my current setup does not present a wholly comparable situation given the asymmetric foward-of-the-wall-plane location of the 40" flat screen, but forget the flat screen for a moment. Prior to treatment of the wall section immediately behind the flat screen with the GIK 244 shown, that space was partially occupied by a plexi-fronted, framed Cezanne print measuring 25"W x 22"H. Comparing sonic output with the print in place and that same section bared (it's wood-siding wall) resulted in better left-to-right channel balance and a more spacious and dimensional right-side presentation with the print removed, i.e, on bare wall. (It's even better--considerably--with the 244 in place.)
Or let's take the second photo's situation of a large flat surface positioned nearer wall center, in this case a ceramic-tile-and-glassed-firescreen chamber of reflective horrors. Although well behind the plane of the forward-radiating speakers (though bass port output emerges from enclosure rear) and at some lateral distance from them, that large surface "flattened" the fore-to-aft soundstage, smeared individual imaging, and buried low-level detail, all of which was considerably improved by the placement of the horizontal 244 shown in Photo 1.
(Note: My preference would be to replace the Kitchell print above the fireplace with acoustic treatment. But this is a shared, very lived-in living space in which I wish to maintain at least a modicum of domestic peace. I may, however, look into a custom-sized "234" to cover the flat screen during serious listening sessions.)