What's the problem?
do you check for an OU on every box if cereal you regularly purchase? Many don't. They should but they don't. Now say the 9oz box is has a kosher symbol, 12 oz doesn't, but the 16 oz does. Can you see how that might be confusing? Would if the case of 1.5 oz do but the 1.75 oz ones don't and they have an identical label.
It's more if a widespread issue and the consumer should be aware. You also run into a similar issue where a product one region is certified but in another region the same product is not certified. Often the only solution is to decertify all of it.