That's not the issue. The issue is what was in print back around the time of the movies. C3PX has said the vintage trading cards have 4-Lom as the droid and Zuckuss as the alien. I want to know how certain he is of that, like does he have a card he can look at to confirm it, because memory can be a tricky thing.
Yes Kenner probably made a mistake, but I'm concerned here solely with what ended up in print in that period, not why it ended up in print, mistakes or otherwise.