That.
I started a trip a few days ago arriving 8h early at the outstation. I introduced myself to the check-in desk since the N-3 flight to CDG was already delayed, would depart 1h later, and my evening flight cabin was already quite packed. Simply offering to board an earlier flight to free up a later seat since I was traveling HBO was met with firm rebuttal, followed by a four-figure repricing proposal. I wasn't even asking for an earlier long haul departure (which doesn't exist on this route) so 0 gain for me, and potentially an extra sold seat for the airline... but even then, it was a big no-no.

While I understand the rationale behind not offering free change for single-leg trips where there's always a chance the customer will fork out big bucks, not doing it for feeder flights is beyond understanding. I used to propose to board an earlier plane all the time before covid, with maybe 50% success rate (not counting precisely since it has low practical consequences). Now it seems conditions are getting stricter -- how inflexible the 14h ulti benefit implementation is confirms this Zeitgeist.