I had a read up on the rule change in 2017 and it appears it was in part due to a keeper (Sam Harper) being concussed and the Vics being unable to sub him for a keeper they had sitting on the bench... Sam had been hit with the bat so the concussion was pretty obvious to all. However, it notes that the concussion substitute wasn't yet in existence. I'd say the concussion sub pretty well covers the potential reason it was changed in the first place that it's pretty well redundant already and could revert to what it was.
It does also mention that the umpire must agree to allowing the 12th man to sub in for the keeper to prevent the rule from being exploited, but given Pant had a bump on the arm it seems the umps are pretty lenient on letting it happen. Could you imagine the uproar if the ump said no use one of the fielders already out there, which is the way it was previously and makes more sense to me.