I have found that in many optimization problems, there is some sort of "local symmetry" phenomena going on. For example, suppose we have a 'nice' function which has $f'(x)=0$, then we will find that around the points $x_o$ in domain where $f'(x_o)=0$, the function's graph is symmetric about a vertical line passing through $x_o$. Even in higher dimensions, we can see this phenomena, for example, see this recent question posted and it's commentary. Here is another problem where I use a similar idea.
Is there some fundamental mathematical truth going on here?
I have learned group theory and that's suppose to quantify our description of symmetry but I can't seem to make a connection of the ideas taught in it and what's going on here?