I can understand at peak times if there are trains every minute or so.
Otherwise it does nothing but infuriate passengers (who may next time
choose to take their cars).But even five minutes is a pretty regular service, it has to be said. I
also doubt that anyone would go back to their car for the sake of being
kept on the platform.

5 minutes seems a long time when a train could have waited 5 seconds
for passengers to cross the platform. There were no Jubilee Line trains
immediately in front so it must have been one turning around at Wembley
Park.

They might not be tempted to take the car all the way in, but might be
tempted to park close to a Metropolitan Line station (if that's allowed
anywhere now) eg might use Preston Road instead of Kingsbury because of
the problems of interchanging.

btw, I drive to a station because the service there is far more
frequent than my own local National Rail stations.

At Finsbury Park, it would be nice if FCC held trains so people could
change from a Kings Cross service to the ones going to Moorgate (and
vice versa). In practice, it would be impossible and could delay other
services (including GNER and Hull Trains) that would in turn mean other
trains lose their paths. Chaos!

I have found that they usually give passengers time to cross where the
trains hit the platform at the same time.