I think, with hindsight, that this hits the nail on the head:
Also, the wording from RDGs press release re the increases is:TfL knew that the TOCs were likely to lose out if Outboundary Day Travelcards were abolished so it was just a matter of waiting for RDG/DfT to do the sums and come back with a sensible compromise.
This says to me that the TOCs (sorry DfT) will gain where the travelcard is sold further out.The proposal also includes a one-off price increase on Day Travelcards for travel from stations outside Zones 1-6 as part of a National Rail ticket from March 2024 (on average 3%) which will be in addition to any general regulated fares increase at the time.