When I am Chief Ref the only reason I would have to go short on a race is if we are running behind - and that would be announced on the line. This sometimes happens if there is a course issue or crash in an earlier race that causes a course closure. No one likes to cut distance but it is sometimes necessary, and should be communicated.

Generally accepted practice among officials for a timed event is to extrapolate the lap times. How this is done depends on the official - I tend to go at least halfway through the race so we get as accurate a time as possible. One consideration is the need to show laps to go a couple of lap before free laps end (last 8k). Ideally on a 1k course I would try to flip to laps with about 10 to go.

Not sure why this race was so far off. If done well in the end the race should only be off +/- a couple of minutes.