This is not an uncommon event in the North Sea if there is a fault with the u/c retraction/extension system.
As to ditching, I would agree with previous posts regarding insignificant effect on the actual ditching process but improving stability on the water.
I don't have any evidence to back up this view as I am not aware of any trials being carried out. As far as I know the only trials relate to a/c stability on the water and not to the actual ditching process itself - and these are only with scale models.
I'd rather have the gear locked down than locked up.