The initial height of the crossbar and the subsequent heights to which the cross- bar shall be raised shall be determined by the Games Committee, and shall be announced to the competitors before the commencement of the competition.
and
Unless there is only one competitor remaining who has won the competition:
(a) the bar should never be raised by less than 2cm in the High Jump and 5cm in the Pole Vault after each round; and
(b) the increment of the raising of the bar should never increase.
The NCAA rule book says
The starting height of the bar and each successive height shall be
determined by the games committee and/or jury. It is recommended that the
bar be raised in increments of 15 centimeters, but never less than 5 centimeters
or as provided in Rule 7-1.6.
I guess part of the issue is a matter of syntax. I read the entire second sentence as a recommendation, I guess the NCAA interpreted the first half of the sentence as a recommendation and the second half as a command?