I never stated there was a standard for this and was speaking strictly about the center I have worked at the ones I have been diving with. I fully agree with having a MOD label on the cylinder. I also never said to NOT analyze.
I always analyze my own cylinders. It is my responsibility to make sure that I know the gas I am about to dive with.
I stated some DCs have green and yellow labels on Nitrox cylinder. These labels do not state the percentage but state that it is for nitrox. Now lets say a blender fills the cylinder, measures it and determines it is 32.4% and labels it as such. Two days later I come to dive and get that cylinder. No way in hell I am trusting that it is 32.4% without verifying it for myself. Often times I have seen a cylinder labeled one way and be off at dive time by 2%.
Now what could be the cause of this? Could be it was not analyzed properly to begin with or it was analyzed too soon and had not yet homogenized properly. It could be the blender was doing multiple cylinders and put the sticker on the wrong cylinder. Humans are prone to error and if you do not check a cylinder prior to diving, it is a trust me dive.