Especially when you factor in how little experience on type in role many of those crews will have - building hours ferrying in the N Sea is not in any way the same as operating the aircraft in the SAR role - with so few training hours it is going to be on-the-job training which is not actually training (where you make things tricky for yourself to build skills) it is just getting the job done and pretending these are quality training hours.
Yes, a trained pilot can hold a hover looking through a piece of perspex, but how accurately? Within 6 inches or so when you have a winchman trying to get to a casualty 200' below you - there is hovering and there is precision hovering - the latter takes the best references available, especially in shi*e conditions.
Perhaps the 189 will be as good in the maritime environment as the 139 - oh dear, how long did they last at Valley?