Sure it may not be planned (though some certainly are), it may not be deliberate (again, though some certainly are)
If it was ‘planned & deliberate’ then they would be diagrammed for a 5 car, they aren’t, they are diagrammed for 9/10 cars hence the ‘shortforming’. You could probably stretch at a push ‘planned & deliberate’ to include control choosing the actual diagram to short form but as alluded to sometimes they don’t get a choice, especially if it’s a last minute failure.
Wow - I don't think I've come across this sort of desperate message in that a service should not be shortformed. Sounds like a 5-car IET on the 12:03 from Paddington to Penzance is nearly a case of a police assistance waiting to happen!
Not really, it’s more a reminder that if a shortformed formation is necessary then it’s a case of trying to share the pain around.