Most likely this is because the camera has written "35 mm" in the EXIF:LensModel field. The Metadata panel shows what is in the EXIF:LensModel field, whereas Develop uses the lens information written by the camera in the proprietary MakerNotes section.
Camera manufacturers and Adobe both contribute to this confusion. Manufacturers could put the same information in EXIF as in the MakerNotes. And LR could show in the Metadata panel the information that Develop uses (which is what anyone ever cares about).
See this thread for more details: Re: LR Full Lens Info . As I wrote in that thread, you could file a feature request for that, but based on Adobe's complete lack of attention to Library metadata the past six years, I doubt they'd ever change the behavior.
So would I be right in saying that this is consistent with ALL 3rd party lenses on Canon?
I only have one 3rd party lens, and for me with this lens it shows the same when shot with 5d, 6d & 7d.