We have been lied to.
There are many secrets developers keep about their games, but not everybody can live peacefully with them. Dragon Age Creative Director John Epler confessed that horse sprint in Inquisition just looks faster but doesn't actually make you move quicker.
He added that he had to "try to make horse sprint feel faster" for three whole days of development. And it worked as many players haven't noticed the lack of difference.
If you've just started worrying about all the time you wasted, then don't: Epler reassured the fans that riding a horse is still faster than walking.
The fact that it's been almost nine years since Inquisition came out and this little detail has been fooling players all this time means the job was done really well.