My, crappish, theory; EG Mac is, or soon will be, taller. Teenage Pony Macintosh was just about the same as Younger Filthy’s height, and still noticeably bigger than most other ponies. So Mac has a few years to go till Filthy has to look up at him. For all we know Mac could grown up off screen.
Wonder if there will be even taller characters in EqG.
‘Canon’ word is not applicable here. I think you mean ‘EQG X and pony X are two different characters’.