It seems like you figured it out yourself but doing 2 x 10 rather than 1 x 20 allows you to use a load that provides sufficient stimulus to be useful for a speed-power athlete. Hormonal (endocrine) response is due in large part to the load used and a load that you are capable of doing 20 reps with is too light to be useful for anything other than muscular endurance (which isn’t too important in a general sense for speed-power athletes).
ELITETRACK Founder