I’d offer that installing the galley unit reinforces the galley floor. This may be a problem for those who don’t opt for it. I haven’t had any problems, though I would’ve reinforced that area with a piece of fiberglass had I known.
Five gallons of water is a bit over 40 lbs. Seems like the galley floor could easily handle that w/o additional reinforcement. Perhaps you had the bad luck of receiving an inferior piece of plywood.