If you want a serious answer it’s because these two games had 1:1 texture replacements. As a matter of fact I think the total count of marines textures is a single digit like 6, or 7. Most of which were Bungie Chicago(?) employees… It doesn’t make sense to add in a script to randomly change textures since it wouldn’t be backwards compatible and really defeats the purpose of what CEA intended to be.
Campaign Evolved is a remake and takes this into consideration. The UNSC should reflect it being a military wing of the UN/UEG, not just one spot. You’d have seen a lot more of this back then if the tech was better setup for it (it was to a degree but not to a degree worth spending insane hours on). This is a non issue and better fits the world of Halo (unless it was a local Militia on Reach or in Nairobi or something). If it was Johnson or Keyes like the show then yeah, definitely worth saying something.