Do you think that an 11 year,or even an 18 year old for that matter, have enough match experience to know all the rules and application of the rules even if they do pass a test? This is what it really boils down to if you think about it. How many debates and different views do we have in the rules section over stuff we "all know" the answer to.
And yeah maybe there does to be a height requirement......if you have to be in position to make a call, how can you make the call if your view is blocked by the shooter. Height could effect the way the time is recorded on the timer. You always see the RO's hold the timer about shoulder high. Remember its an 11 year we are talking about.