Platform 3 was always used by trains towards Bradford/Leeds/Harrogate until it was closed in the rationalisation. Then the island platforms 1 & 2, which used to be served by trains to Manchester and Huddersfield, became used by Bradford trains on platform 2 and Manchester trains on platform 1, and has remained thus until the present day - a situation now becoming unacceptable with the increase in trains [when the rationalisation took place, there was just an hourly service in both directions, with trains to Huddersfield [and Penistone] having been withdrawn.
When the Calder Valley was turned over to dmu operation in 1962, the steam-hauled Bradford/Leeds portion working at Low Moor was abandoned, allowing the closure of Low Moor, as the dmus could easily reverse in Bradford Exchange with little extra journey time being necessary. The opportunity was also taken to combine the existing Bradford Exchange/Leeds/Harrogate service, [which originated with the first dmus, the Derby Lightweights introduced c.1954], with the new Calder Valley service, thus creating a Liverpool Exchange/Manchester Victoria/Bradford/Leeds/Harrogate service.
It worked out very neatly - trains departing Liverpool at x30 past the even hour, x25 [and every hour] from Manchester, arriving Bradford x30, departing x35 past the next hour, arriving Leeds Central x57 and Harrogate x25 the next hour; returning at x35, Leeds x00/06, Bradford x25/x30 and Manchester x30 the following hour.
Most services during the day ran through to Harrogate but were curtailed at Leeds during the early morning, after tea-time and all day Sunday.
This pattern was then cut-back around 1965-66 as you say -[I'd gone away to university at that stage and lost touch with the local scene], and became the basic one train per hour, Manchester to Leeds you mention.
Further information can be found on the RailcarUK site:-
https://www.railcar.co.uk/type/class-110/operations