gotmiki, a quote from the link that you posted
"The 25M gives you a zero that roughly matches a 300M zero based upon trajectory and bore access. This is the standard zero and allows the firer to hit a man sized target when aimed center of mass from between 25M out to 350M."
Maybe that is why they chose it for the standard range for the ARCO, RCO and MRCO scopes, which are not the sort of scopes that you would adjust 'on the fly' in a combat situation, hence why they do not have pageup/pagedown adjustments available.
And, just for your information, I do have extensive experience of shooting assault rifles - at 100, 200, 300 and 600 yds.