broadcast quality pictures...???...

I've worked in the television industry for nearly 20 years; and think you need to know there is no such "standard" as broadcast quality. It is nothing more than a meaningless term used by various sales types and promoters to "impress" the uninformed.
Almost any type of video can be "broadcast" - even lowly VHS tapes (think America's Funniest Videos) and fuzzy videophones (think of early coverage of the Afghanistan conflict).
Perhaps your "friend" was trying hard to impress you with his so-called "knowledge". Though I seriously doubt he "knows" something that any broadcast engineer doesn't already know.

BNC is just a connector--generally for pro use, but used on some consumer gear (see, e.g., Theta). I think you are talking about RGB HV--the HV just stands for Horizontal and Vertical sync--generally requires 5 cables/connectors. Perhaps marginally better to separate out the sync signal, but I think most component is sync on green, and I doubt you would be able to tell the diff.

There isn't any more to the b/cast signal that you can get using a standard NTSC tuner (for normal b/cast) or HD tuner (for HD broadcasts). The specs are public for both standards.

I'm also pretty sure the big three auto manufacturers don't have a 500 mpg carburator hidden in the vault either. ;)

What your friend may be talking about is copy protection associated with HD content. You can't run HD digitally into copy devices that allow unrestricted duplication (HDCP). It won't allow a digital signal to be run into a computer and dropped onto the hard drive, for example. That doesn't mean that with a compliant HDCP DVI input on a display device that you can't take advantage of the digital signal when you view the program. Just means you can't copy it for grandma.

the reason that you do not see broadcast quality video is because actual film can better show depth of field and texture that that of dumbed down broad cast. It is similar to music compression technology.