The spectrograms on this site have a lot of spectral leakage. This can be improved a lot by applying a window function (blackman, hanning etc). It doesn't seem like the author does this.
Applying the Hann window function eliminates all the spectral leakage, but it also makes the image rather dull and precise, very similar to CWT. You've made me realise that the intricate patterns seen on violin spectragrams are the result of interference of the spectral leakage from main harmonics. It doesn't mean the patterns are fake. It means the patterns emerge only when the input sound is transformed a certain way (FFT with the rectangular window).
