The Mk3s were withdrawn four years ago (though they could stop at Shotton, and did on the odd occasion). That does rather underline the point that the current timetable is an ancient relic which should be consigned to the history books.
Why does 1D32 not call at Abergele, while 1W95 does? That can't have anything to do with former loco-hauled diagrams.
Part of the reason for the bizarre service pattern seems to be that politicians like having a direct service to/from each conceivable destination. So Llandudno has a token train from Birmingham and a token train to Cardiff.