From my time in the audio hobby and profession, I feel speaker "speed" has much to do with the response time in moving with the very first note/electrical impulse. The trailing edge of a note is easier for a transducer as it is already in motion. However the leading edge begins with the speaker/transducer at "rest", and the possibility of the transducer being slower than the electrical impulse being sent to the transducer. (sorry for the "transducer" word, but I do not put electrostatic and planer speakers in the same category as push-pull standard types of speakers).
Interesting question and answers.
Interesting question and answers.