I have never seen a boat that size without a splash well.
A. This is a 25", not a 20" transom.
B. There is a splashguard available that I've seen on a couple of the
21-footers, most recently on the 2120 pilothouse that shares the same
hull. I see no need for it.
C. I began boating 50 years ago on Long Island Sound, which can get
plenty rough. My outboard boats in those days have completely open 15"
transoms.
D. In the photo on the Parker site, the boat is equipped with a 200 hp
engine, one that weighs more than 100 pounds more than the one I have.
Also, there are two lardbutt guys sitting on the gunnels near the stern,
and another guy more amidships.
E. There are dozens of boats that size and even larger with open transoms.
F. I owned three SeaPros with 20" transoms and only one of them had a
splashwell. Only once did I take any water over the transom out in the
Atlantic Ocean.
It's not an issue, except maybe to inexperienced ocean boaters.