Thanks for the specs.
Is the primary purpose of the gun to stop attacks by small watercraft?
The 57mm made a comeback 30 years ago on the Canadian Halifax frigates supposedly as dual purpose anti aircraft/anti ship, although knowing the Canadians the calibre may have been chosen as non-threatening and too small for shore bombardment
There was also some promotion at that time of the calibre as a longer ranged CIWS than Phalanx, although most thinking now is that 35/40mm is a better choice.
It was chosen for LCS because weight saving was important the those abortions were ever to make 50knots, now its probably there as legacy because the Pentagon doesn't want to admit they chose pooly.