Perhaps the difference is that BS1363 was designed to have shutters from the outset, rather than some kind of a retrofit. They were part of the original design.
I've really never seen any problem with the shuttering system used on BS1363 and it is very unusual to see it jammed or stuck open.
It just seems to work very reliably.
As for the cost, I don't think it seems to add much to it at all. Although, that being said, the fittings here are generally more expensive than US/Canadian and Continental-European counterparts. Our prices seem to start at around the mid-range of NEMA / CEE 7 prices.
