I disagree. It is disruptive to service patterns to split the Southport service between 2 stations in Manchester, and sending any Southport trains to the Castlefield line is likely to have an adverse effect on future service performance through the route from Salford Crescent to the Castlefield line. It is wrong for a small town 40+ miles away from Manchester in another metropolitan conurbation to have been given preferential treatment (as a result of lobbying) over the residents of North Trafford, whose local line will be henceforth only be permitted to have a (fairly useless) 1 tph stopping service.
So what you're saying is that a relatively low-used local stopping service should have priority over a much higher-used regional service?
Castlefield isn't just about Manchester, it's about the North's entire regional service. Therefore there is no good reason to prioritise views of people who happen to live within Greater Manchester. It would be equivalent to saying "Thameslink is for people from Mill Hill Broadway, not Bedford".
Talking of the CLC stopper we have:
Warrington C: will use the half hourly fast
Birchwood: will use the hourly fast
Glazebrook: about as useful as Dent, Bescar Lane and the likes - in the middle of nowhere and very low usage
Irlam, Flixton: probably the two losers, but may receive calls in the fast(s) and certainly used to in the morning peak
Chassen Road: quite near Flixton; due to the presence of a large park has a very small catchment indeed
Urmston: will get a call in one of the fasts I believe
Humphrey Park and Trafford Park: quite close in and well served by buses, unlikely to be busy unless they were Metrolinked with 5tph
So not practically a huge loss, compared with the Liverpool side where things look more like the rest of Merseyrail.