Besides the recent closure of the booking office and general sheltered facilities, the early closing of Llandudno has been the source of complaint since the refurb of the station in 2014.
There seems little rhyme, reason or logic in TfW's staffing hours and they bear little relation to passenger usage as the following indicate for 2021/22 from ORR:
Flint 188,000 passengers; 0615 - 2115
Colwyn Bay 207,000 passengers; 0615 - 1915
Llandudno 240,000 passengers; 0830 - 1500
Llandudno probably has a higher higher of enquiries from visitors regarding train times, fares etc. but then TfW, reflecting its masters, has little interest in promoting holiday or excursion traffic.