Given the context of service weapons, I do not understand your quibble. Are you sharpshooting his use of "several years" instead of "many years?" Are you relating your experience using an unissued model of optic during Mil or LE service?
Comp M2 and M4's represent only part of the USGI RDS body; and another brand in particular had a long way to go during the time of the initial fielding of M68's. That other optic may work fine for many on the outside, but it required significant upkeep and user modification to fit the needs of those services; which fits rather well with Beat Trash's assessment.