Does Mount Stupid refer to the observation that people tend to talk loudly and confidently about subjects they barely understand (but not about subjects they understand so poorly that they know they must understand it poorly)? In that case, yes, once you stop opining the phenomenon (Mount Stupid) goes away.

Mount Stupid has a very different meaning to me. To me it refers to the idea that "feeling of competence" and "actual competence" are not linearly correlated. You can gain a little in actual competence and gain a LOT in terms of "feeling of competence". This is when you're on Mount Stupid. Then, as you learn more your feeling of competence and actual competence sort of converge.

The picture that takes "Willingness to opine" on the Y-axis is, in my opinion, a funny observation of the phenomenon that people who learn a little bit about a subject become really vocal about it. It's just a funny way to visualize the real insight (Δ feeling of competence != Δ competence) in a way that connects to people because we can probably all remember when we made that specific mistake (talking confidently about a subject we knew little about).