There should be a dialog box of some sort that pops up when a display is believed to be incompatible. The user should be able to acknowledge that and attempt to display the 3D content if they wish.
I think I have to agree with this opinion. I've been following this discussion trying to understand the issues. I wanted to form an informed opinion.
I don't have a 3D TV, nor am I likely to buy one for many years. We replaced our main TV within the last few months, and specifically chose not to pay more for a 3D TV. (My personal opinion is that 3D is a fad that will fade, but I've been wrong before and will be again.)
Having seen many post over the years with people having HDMI handshaking and 1080p/24 issues, I have to say that I don't think you can count on AVR or TV manufacturers to follow any set of standards consistantly.
They want a seamless process for their customers. They want it to be easy. However, because they have to coordinate/communicate with other company's units, they just can't control the whole process. While that means more work and support for DIRECTV, I think that is the only customer friendly option they have is to allow a (nonsupported) work around for customers to force play the 3D programs.