For a time, I too shared the idea that multiplication makes things bigger. I don't remember if it was taught this way, or that was just what I inferred on my own. In any case, it was an absolutely terrible way to think about it. Sure, it was fine until fractions. But unwinding that poor mental model was a jarring, painful event. I remember to this day banging my head against the figurative wall, crying literal tears trying to understand how multiplication by a fraction made something smaller.