As mentioned in other comments, this is just a concept, they haven’t built it
But it’s a pretty cool concept. Video here:
https://m.youtube.com/watch?v=Q8TUTp0_D-I
The mounts in the Horizon games on PlayStation are even better as a concept, as they let you actually try it on. And they're probably as close to implementation as this.
https://horizon.fandom.com/wiki/Category:Mountable
The mounts in the Horizon games on PlayStation are even better as a concept, as they let you actually try it on. And they're probably as close to implementation as this.
https://horizon.fandom.com/wiki/Category:Mountable