In terms of dissolved minerals sure, but there's two important distinctions to make. The tank isn't just accumulating deposits, there's an anode rod inside that

In terms of dissolved minerals sure, but there's two important distinctions to make. The tank isn't just accumulating deposits, there's an anode rod inside that's designed as a sacrificial element to protect the tank itself from corrosion. That anode rod gets consumed over the course of a decade so while it's not much, it is being introduced into the water. Also those deposits provide a porous substrate for bacteria to grow on and the heat will help things along.