I think it's worth noting that it isn't an issue of "honesty" or "transparency" nobody is trying to cover anything up or hide things from people. It's just a failure within the way that information is presented to passengers (and staff, particularly platform staff!).
But there was no official announcement of this delay / cancellation at Altrincham, the board just went from the train being due at 15:38 even at 15:50, to advertising the 16:36. After a while Northern's disruption page stated that this service had been canned at Stockport due to a fault. Fair do, I'll wait for the next. But just when the next was due to leave Manchester, that got canned to stating problems with the traction. It took another half an hour before the site eventually said the original train had failed between Stockport and Altrincham and disruption would be until at least 19:00.
Yes I've noticed this can be a real issue at some stations, I
think it's related to the source of the data (I notice it happens around here on bits of line that are driven by signallers inputting times rather than having actual information on where a train is), services just getting later and then dropping off the board with no idea what's actually happened to it. I've rolled into Redcar Central on late running (often not even that late, perhaps five or ten minutes) trains and the departure board is advertising the service after ours already. Obviously it's something that should be tackled but hopefully it will eventually be a thing of the past as there are fewer and fewer areas that are effectively "dark territory" outside of the local boxes panel!
This is possible. The "one source of truth" passenger information system that powers TOC apps, station departure boards, and some third party apps is called Darwin and does support associations, which will auto delay the outbound based on inbound. These can be changed live on the day to reflect set swaps.
I experienced it myself at Waterloo last weekend - the inbound was late, got a bit earlier while it skipped stops, then got later again when it got stuck in congestion between Clapham Jn and Waterloo. Evey delay change to the inbound was immediatly reflected in the outbound working with an offset for the turnaround time.
Yes it's disappointing that the industry doesn't ensure that this is rolled out comprehensively across all services. It's a really vital tool in providing accurate information during disruption because it captures those delays that will be caused by late running inbound services. Not having those links generates the delays that passengers find most annoying/unnerving where their train just gets later and later until it ticks over to just being "Delayed". When in reality it would be perfectly possible to have a fair stab at how late it's going to be if only the inbound was associated to its next working. Even in places that it's fairly straight forward terminus like Saltburn where the Northern unit in is going to be the next Northern unit out again it isn't done for all services only if control spot a delay and link them together (though it is done at the other end in Darlington for all services so delays are correctly carried over to the next service!).
All that criticism being said it's also worth remembering that we're not the only place that struggles. I think the worst case of bad information I ever had was in Warsaw waiting for a train that was coming from Krakow heading towards Mockava (in Lithuania). Get to the station at around 0650 for something like a 0710 departure and then at 0705 the train is suddenly delayed by 80 minutes or so. Now, there's no way that PKP suddenly realised at 0705 that the train was going to be 80 minutes late, they must have known some time in advance but was that communicated anywhere? Nope. I've never experienced anything as bad as that in the UK even in the time before we had access to things like RTT!