It's just the same as any modern top quality servo drive can do the duel encoder feed back but it is not widely used because of the added cost
Have you used or installed this to know how well it works or even seen a machine where it is being used, I know of a few machines that use duel feed back but they cost between 250K to 500K
I don't think to many hobby guys will be using a duel closed loop anytime soon a lot can dream