Dore-Castleford is a particularly poor example: let's read what the HS2 plan actually is:
https://www.hs2.org.uk/stations/sheffield-midland/ - it's a link from the HS2 to Chesterfield and Sheffield on the existing line. It reads very much to me that you won't be able to have a direct Sheffield-Leeds HS2 service, or if you did it would be on the existing tracks.
Unsurprisingly that page extols the virtues of using Sheffield Midland - "It also allows for core HS2 services to run into Sheffield Midland without necessitating the cost and environmental impacts associated with building a dedicated high speed station in a dense, urban environment, whilst at the same time allowing an easy, cross-platform interchange to places across the city region by rail..." - try reading that whilst thinking about
Curzon Street..