Just a thought carb, but do you think these 72 places will
a) be undersubscribed or
b) oversubscribed?
If it is a), then you are right and they are missing out on some untapped talent. However, if it is b), then presumably they face the potential of having to discriminate between too many candidates to select the final 72. Setting a narrow age band is one way of reducing the number of applicants to a manageable size. Another is closing the door when you have the number you require; they obviously intend to do that as well:
http://www.ctc-mcalpine.com/application.htm
Tough if you miss out, and we all feel for you. Gives you more chance in the JMC competition though.