No. The flanges are strictly cosmetic. If the penetration in the finished surface needs to be watertight, you will need to use an approved silicone product for application.
Does Dearborn Brass/Oatey offer any shower conversion products for a claw foot (tub on legs) bathtub?
You can easily transform the claw foot tub into a tub and shower with #R100 Kit. View the components in the kit.
Does installing a Sink Hole Cover create a water tight seal?
The Sink Hole Cover will not achieve a water tight seal on its own, and an approved silicone product will have to be applied in between the sink surface and the Sink Hole Cover.