Yep, so did I.
I don't necessarily think the "3D" diffusion (which is what the rest of the industry calls 2D diffusion) is a great choice for the ceiling though in the case of a controlled directivity horn with tight vertical directivity (which I presume the one LTD showed has) then anything including bare ceiling probably works about as well as anything else. In the case of speakers with wide, constant directivity in the vertical plane then 2D diffusion (possibly with some splitting action) to throw some energy onto the sidewalls is probably better. Although, whoa, this just made me rethink my ceiling plans. Thanks for that! Time to go back and look at my off-axis responses. LOL.