You didn't really do a complete short field take off imo. A short field gets the front wheel just off the ground and then you nurse it into the air when it is ready with an appropriate amount of back pressure on the control column. Then you accelerate in ground effect and then climb out. This is what I was taught and the POH says to "lift off as soon as practical".

A lot of short fields I've done in Oz are off gravel runways so it's better practice to keep your momentum from the taxi than chill with brakes on at takeoff power sandblasting everything anyway. I know you were on paved but that's not usually where 'realistic' short fields occur.

For the purpose of the experiment though, I feel you should've done your normal take off either from a standstill too or commenced both at the same taxi speed. There would be a taxi speed where a shorter take off roll is achieved than starting from stationary with brakes applied. What speed that is, I don't know however. Just my 2c :).