Certainly other vendors offer ostensibly sealed back boxes for their invisible speakers either Metal (fire proof) or wood/mdf.
Certainly other vendors invisible speakers are easier to install and attach to the *studs* rather than the 6 screws that this model uses to attach to the sheet rock. Also others only have to plaster the (non moving) edge, not the whole face (Diaphragm)of the speaker with 1/6 of mud. I suspect that the competitions models that are thusly described probably sound better as well!
I think this new entry product from Nakymatone will have a rough go at it.