Interesting pics Pieter. The more you study history the more you realize you shouldn't say NEVER. Once you realize that the guys on the front line are fighting for their survival, it becomes obvious that there are lots of undocumented exceptions. Your example in this thread is non-medics wearing field medic yokes. You have documented your statement with the photos which is difficult to dispute.
I would also suggest that these are exceptions and not the norm. Using the Iwo Jima pic as an example, the guy in the bottom right is using medic yokes, the guy in the top left is wearing USMC suspenders, the guy with the patrol cap doesn't have any suspenders. I do not believe the wearing of medic yokes by non-medics was done at a unit level, but rather solely at an individual level. I would also point out the grunt with the yokes is wearing TWO cartridge belts rather than only one - not something I have seen anywhere else. Obviously we can say that it was dones by those that were there, but certainly was not a common practice.
Please keep the pics coming!
'43 Dodge WC54
piles of smelly green stuff
a couple of band-aids