Problem with these things is that they are indeed packaging errors, but if the set were broken up you have a number of completely normal coins. This, to error coin collectos, is of no interest.
Now, people who collect the sets with packaging errors might be interested, but they wouldn't categorize their collection as an 'error coin' collection...because the coins therein are not errors.
I've had 60s proof sets with extra coins (1960 with extra dime, 1963 with extra cent) and I have seen sets with coins packaged backwards (reverse side up). I just pass over these as normal sets.