I don't really know, but my guess is that it's probably because they use the MSFS 747 panels, as explained in the rquirements for being able intall/use the 767 (as shown below). Perhaps that's as close as they can get to not having it show up at all.

I'm also not surprised that it's showing in the YouTube video of the CS 767. If we see it, why not him? :)

From the description for the cockpit and cabin of the 767 III:
Some systems use default 747 (must be installed) to provide expandability with community mods