I haven't read the entire thread, but I did discuss this with David Trevalian long ago. His preference was "table" and felt "water table" was put upon us by some gun writer (maybe in the 1920's) who simply did not know any better. Other writers (who didn't know any better) copied it and it is in common usage today.

The term "water table" is common in shipbuilding and the aircraft industry. It is an imaginary line used as a reference point from which other items or lines are measured.