[jcranmer]

I can see why you might think this. It is a quantum mechanical effect, but it has nothing to do with the main quantum mechanical effect everyone knows about (superposition).

Superposition of two states is not preserved by measurement: it's more akin to a (complex, not real) probability you'll find the system of one of the states.

By contrast, resonant bonds are a real mixing of the two states: you don't observe the carbon-carbon bonds in a benzene molecule as either being a single bond or a double bond, you observe them as a uniform bond that's somewhere between a single bond and a double bond (e.g., bond length). Treating such things as a weighted average of various resonance structures is a usable approximation that allows you to predict the structure of more molecules without having to dive deep into molecular orbital theory.