All methods of fitting a bike are 'rule of thumb'.

I've fit thousands of bikes over the years and have seen and heard it all.

Two things have caught my attention. First was this quote: "I seem to rock less" If you 'rock in the saddle' your seats to high. Second, the picture of the Cannondale...is that seat height at which you 'rock' in the saddle?

What is your height?
What is your blue jean size? (length only...no need to know your weight)
What is your sleeve length on a dress shirt?

Oh yea...go to a different shop....