Yes, of course, if one notices that the hashgacha is part of the ingredient panel and that there are multiple ingredient panels, they would look at the others.
I don’t see how one wouldn’t notice that there are three ingredients panels.
Unless you are interested in the ingredients, for allergy or health reasons, many people do not pay attention to these panelsand lists when making their purchases. They scan the package, find the symbol and buy and eat.
Did you see the package?
There are three varieties, as clearly marked on the front, and there is no hechsher on the front. There are clearly three ingredients panels, on the back, one for each variety. The OU is only on the ingredients panel, which to me clearly means that it only applies to the specific product whose ingredients are listed in said panel.
The non kosher gummy variety does not have an OU on the ingredients panel.
To me, it takes extreme carelessness to make the mistake of thinking that all the varieties are kosher, because it should be obvious that the OU is not for the whole package.
Should the OU have a policy to save very careless people from errors? Perhaps, but if someone ate the gummy candies based on how they read the package, they have primarily themselves to blame.