All boats used to have enclosed cockpits with a fixed transom. Most boats had a bridge deck
in front of the companionway
to prevent flooding down below if pooped. If they didn't have a bridge deck
, it was de riquer to fit the hatch
boards at least part of the way up to prevent flooding in susceptible conditions.
boats initially went to the open at the rear cockpits possibly to save weight in the '80s, IIRC.. They offer a no restriction way to drain the cockpit
but I always fear stuff going out the back whether by wave action or it just happens.
So, no it's no big deal to have the cockpit
closed off if you have a bridge deck or put the hatch
boards in threatening conditions.