The parent was pointing out the conflation of action (double-tap to fit, overloading volume control with on/off features) and mechanism (fitting algorithm, physical design of said button). The former is not patentable, or rather should not be, while the latter might be.

It's the difference between going to the patent office with an idea for "an engine that runs on steam" and actually designing a steam engine. See how much broader in scope the first one is?