If you climb on top of the covers, you are still able to call your horse.
On the covers near the building on the east side, you can slowly ride your horse to the edge until in glitches out in jumping position (constantly shaking). Call your horse while it's in sight multiple times and it will finally hop out of its position and automatically travel the direction it is facing. However, its legs lack movement. You can still climb onto your horse, but it would travel very slowly and you would rather ride it using the V-pad.