See original post, I guess?

A lot of the constraints in how airlines can market service levels are imposed by the ticketing aggregation standards and how fares show up in searches. There are also issues with creating differences in luggage standards between regional and long haul flights because of through ticketing.

It’s probably more complicated than it looks from the outside, and all falls into the same problem of overall air travel inscrutability caused by the ‘it makes sense to the people who are in it but looks Byzantine from outside’ problems the original article here is complaining about.

I tend to doubt it's more complicated than it looks.

It's a way to make more money off people for worse service, with the externalities going on people who can't do anything about it.