dhenry:
I don't see a datasheet from an original manufacture stating it's designed to work at other then 'standard' servo update/pulse width control.
Many of the servos are analog: it takes the pwm pulse train through a low-pass filter to derive at a voltage signal (to be compared with a position sensor's output). Because of such, a higher pwm frequency will always work - but a lower frequency may not.
I take such statements as not understanding the question. The site said one must first test a servo for higher framing rates, why would they state such if higher pwm frequecies 'always work'?
Lefty