*Sigh*
I don't know how people don't get that there's a tangible difference in the suspension of disbelief for something like "magic" working in a piece of fiction, and things just being jarring.
So we all know how Hauchefrant died right? A massive spear of lightning to the chest, blood spilled from his lips, and even though we have resurrection magic, he died and it's 'believable' right? It's believable that a hit like that can and should kill an Elezen.
Imagine if next patch. Thancred is in a sword fight, and just takes a sword right in the bottom of his jaw, and it runs all the way through his skull, through his brain, and out of the top of his head, in gory detail. He then proceeds to pull the sword out of his head, and act like nothing is wrong. And despite people seeing it, no-one ever brings it up ever again, and in-fact people go on to say he's just a normal Hyur.
There's an element of consistency in suspension of disbelief. I can believe that Dragoons can jump because you see it, a lot. It's an established thing, they are KNOWN for it. There's no known lore that lets a woman's butt glue itself to a horse, and considering physics seems to work about as one would expect it to, (gravity, velocity, friction, etc.) it's a bit disjointing that it just 'is', and thus to a lot of people it looks wrong.
Is it a nitpick? Yes, it is. But it's not an invalid observation.
Given the time for attention to detail, adding detailed and consistent riding animations would be really neat. Just deciding to remove unicorns because unicorns aren't real wouldn't be neat at all.
See the difference?