I have had it confirmed from someone inside the Friends of the Settle Carlisle Line that Northern have indeed withdrawn the Horton/Clapham and Ribblehead/Bentham ticket inter-availability concession. It is something that the group is campaigning to get reintroduced.
To me it looks like yet another example of the railway trying to extract as much cash as it can from existing passengers, even at the risk of losing those passengers, rather than doing things that would attract new custom.