I agree if your only seal is around the screw. However, on a larger bedding surface like a teak rail, you water proof the surface being beded, not the screw hole. I would prefer to see lag to thread bolts be installed and eggcorn nuts used inside. That way both the bedding surface and the fastener can be sealed as described. Also with a bolt, a little countersink on the exterior of the hole filled with polyether will create a great seal.