Just a "broken down train" is utterly useless information.
At least after posting the question on here, I now know the reason why. But I would have liked to have known the reason why earlier today when instead I had to go and get a bus instead.
I assume there are a nice load of drop down menus for staff to select reasons for delays, and I notice quite a bit that the reasons for delays aren't very helpful when it just says 'broken down train' or 'signal problems' without saying where, allowing even someone without an app or access to this forum a reasonable chance of a guess at least.
The broken down train 'reason' will often be attached to other trains delayed, but if you don't know where/when the broken down train was/happened, it doesn't give much of a clue as to whether the delay is as it is (i.e. it started late) and the estimated time will be correct now, or that the broken down train is potentially going to cause further delays - like it's still there somewhere and the time on the board may change.
To be fair, sometimes GTR will give manual announcements that give more detail, and they can remove all services and just show the ones running during extreme disruption, but there are definitely flaws.
Unless someone has direct access to control (or someone that does) it can be frustrating as if I suspect there's likely to be an ongoing problem, I want to switch to my plan B travel arrangements, not hang around.