Hi Barbara am sure you are absolutely correct in your assessment but never really thought about injecting into the muscle would be quicker as only advised with putting bolus sub cut in the belly.That may only be relevant timings for his body with the insulin he uses and the exercise/training/sport he does. I would expect rugby and football players to have very muscular legs probably with particularly well developed cardio vascular system, which may make his their more responsive to insulin than say yours or mine.
Similarly always inject basal into bottom but was advised could put it into thigh but I do have a lot of muscle in my legs and just find it more uncomfortable if I inject there.
HAGW.