Yes, normally if a bus isn't running at all (or if it is running but for whatever reason it's not tracking properly) real time displays will show the scheduled departure time (as a time rather than number of minutes) until that departure time has passed.
Some systems allow operators to intervene and put 'cancelled' up if they know a journey is cancelled, but not all local authorities give operators access to do this, not all operators have the staff resources and inclination to do this.
(I don't know West Yorkshire very well at all, so have no idea just what system/s are in use there or what the local policy / practice is.)
A bus appearing 'stuck' a number of minutes away suggests that the 'stuck in traffic' situation or possibly breakdown on route is more likely. The system isn't a crystal ball - it will assume that if a bus is X distance away, then it should normally take Y minutes (at that time of day) to get to this stop, and it won't know whether the bus is just at a bus stop or whether something else has happened.
I suppose it would be feasible for a system to show something else if a bus doesn't move at all for X amount of time (some of the displays on the railways will change to 'delayed' if the train stops for too long) but I've not met that on bus RTPI displays.
Likewise, the system will assume that if a bus is approaching a terminus and isn't so late that it won't be able to leave on time, that it will leave on time. The system won't know if there's a driver change-over scheduled and / or if the driver who's supposed to take over isn't there.
The other possibility might be if the bus has gone off-route for whatever reason and isn't serving that stop. The systems are supposed to work so that a bus 'clears down' from the display at a stop once it's gone past. This can occasionally go wrong, and it can get confused if a bus is on diversion, and a diversion timetable / stop blocking hasn't been entered in to the system.
Although in this case, I'd have thought that if there was a diversion away from somewhere like a bus station, then there would be some form of information out there unless it's something that's happened very unexpectedly (like a sudden major road failure or police have closed the road for an incident.)
If you want to put a complaint in, Metro and / or the operator probably have the ability to see the tracking data for that route / journey and see where the bus actually went and when.
