If you look at the DECODED signal, which would be a stream
of numbers, one defining a luminance level and the other defining
a color, and displayed them using an appropriate method, it would
look a lot like an analog signal displayed the same way.

That isn't the way an MPEG is encoded. It's rather more complex.

Furthermore, as most (though not all) color-encoding systems use some
combination of luminance and color-difference signals, it follows that, on a
basic level, DVDs, BDs, NTSC, and PAL -- not to mention JPG -- are very much
alike. Claiming there's an interesting similarity doesn't tell us something
we don't already know.