It seems I am confused.
Journeys from where to where did you have in mind, exactly?
If (as I suspect) you are looking at journeys between Dolgarrog and Llandudno, doubling back at Llanrwst doesn't work.
A passenger wanting to travel northbound from Dolgarrog, basing their travel on tomorrow's timetable will be caught out by that impractical doubleback, I agree with you there. But given how little publicity there's been about the new timetable, I'd expect passengers to either turn up at 0925 for the current through bus replacement service, or at 0916 for the reinstated rail service that apparently calls there (according to RTT and National Rail). The terminating bus from Blaenau will arrive at Dolgarrog at 0905 for a layover until 0955. I'd hope the driver could either call TfW to get a minicab for a passenger that's stood knocking at their door, or (if contracted) take them to Llandudno Jn for a connecting service. With the current state of the platform, no passengers will stand there expecting a train!
Travelling southbound to Dolgarrog looks trickier. I think the most likely ocurrence is that the passenger would be overcarried to Llanrwst North, where the guard could arrange minicab transport back to Dolgarrog.
This hasn't been publicised very well yet, for the "one man and his dog" that use the line on an average day. I can see how this could work relatively smoothly in practice, assuming that there are plans in hand. But as has been discussed, Dolgarrog station isn't very convenient for the village, and most locals will be using the ~hourly 19 bus service on their doorstep instead.