I already have a high detail horse in the form of paladin class mount, BFA collector's edition mount and prestigious war steed from pvp world quests. If you wanted a plain - really plain no armor etc. high res horse, one would be sufficient, having 4 or more of these seems a tad bit overkill.
And the gryphon wasn't any higher detail than the MOP one (even though some people say it was removed?)
The only positive thing is even if they're copy-pasta assets at least it's different assets unlike WOD boars that were 2 models constantly recoloured. In the same vein I'm super disappointed with Lightforged racial mount, it's a recolour of army of the light paragon mounts, doesn't even have different saddle / armor. As a comparison, Nightborne racial mount is a model change from arcanist manasaber / mystic runesaber / any other cat. It's not just a palette swap.