I'd always thought the reason the former Aintree Central had this suffix must have been because it was originally on the CLC system, which had a fondness for naming its station "Central" (plus associations with the Great Central).
It turns out, according to this
Disused Stations article, that Aintree CLC was only named "Central" during the BR era in 1950.
On the same line, maybe the Southport & Cheshire Lines Extension Railway's terminus at
Southport Lord Street should have been named Southport Central, given the station's very central location and the CLC having been the principal backers of line and operators of its trains.
Perhaps "Lord Street "was seen as a more prestigious and exclusive destination, given that nearby smoky, industrial towns like St Helens, Wigan and Widnes all had their Central stations.