Moisture-resistant paint next to bathtub -> sealed/tight?

Hello! We are currently building and I do not want to have tiles on the walls except directly in the shower, not even by the bathtub. My boyfriend and our plumber have just tried to talk me out of it - arguing that where the bathtub meets the wall, it won’t be properly sealed if you don’t tile. Since I have zero knowledge myself, I’m now turning to you. Does anyone have experience with this? Thanks in advance for your answers! Best regards, Cornelia

Moisture-resistant paint does not seal a wall against moisture. There are other options instead of tiles, but that would always be something that is stuck to the wall. When it comes to the silicone joint, you are also right: the paint is not smooth on the microscopic surface, but uneven. I can also imagine that the silicone does not bond with the paint. In that case, the joint could not hold the water.