I did a fresh install of the PTS for the first time just to see what effects the mount speed increase has, and I'm really sad to see that the mount walking animation is simply gone due to the increased mount speed of this upcoming update.
How mount animations work on live
For anyone who might not have paid attention, while mounted there's a walking animation, a jogging animation, and a sprinting animation, just like with our player characters. But (for non-console players) after mount speed upgrade 15 the walking animation disappears, becoming a slow-motion version of the jogging animation. You can never recover that animation and it becomes really jarring anytime you want to walk around with your horse.
I actually started a whole new character a few years ago just to get my walking animation back, and kept him at upgrade 10 to keep some distance from the death zone that is 15.
How it works on the PTS
But on the PTS, our base speed was increased by so much that the walking animation is simply gone, even if your speed upgrade is at 0. I beg ZOS to either adjust the walking animation threshold so that it's in-place until upgrade 15 again (like on the live servers), or just rethink how this mount speed buff is being implemented to begin with (perhaps only buffing sprinting, rather than walking/jogging too?).
It's a shame to see this animation disappear, so I hope ZOS gives this some attention before implementing the changes.
And on a personal note: if you raise the walking animation threshold so that the animation exists again, but make it lower than the current upgrade 15, PLEASE give players the option of removing their speed upgrades so we can choose to set it below that threshold if we want. I'd hate to make a whole new character again just to fix this animation.