Oh come on. Do you think with million dollar development budgets that we never listened to anything? What do you think companies who develop speakers do? Listening confirms measurements and measuring confirms listening. It is always a two way street. Your "stroke your beard" comment is out of line. Just experiment sounds simple, but if you don't understand the basics, like how capacitors perform in a crossover, you are likely to make a flawed experiment and convince yourself of something incorrect. Then you will come on here and tell others about it like it was true.
There is lots still to learn. How to interpret the electrical characteristics of a capacitor and apply that to a crossover is not one of them. There are parameters of different capacitor constructions that some believe are audible. Dielectric absorption already mentioned and mechanical resonances being two, electrical resonance potentially being a 3rd influenced by ESR in the operating range a 4th. A small bypass capacitor will not solve any of those issues, nor make any change that is not swamped by component to component variation.
Do you really think these high end speaker companies have never thought of bypassing large capacitors with a much smaller one to make a better speaker?
When you lack an open mind you may be able to convince yourself your measurements and models are always adequate.
Takes an open mind and discerning ear to realize when one or the other has fallen short, and this topic is impossible to argue online. That's why I make suggestions to audiogoners to experiment inexpensively and come to their own conclusions. Or they can listen to you stroke your beard and tell us nothing is left to be learned.