That is what the texts said when I first started collecting.
But I think that information is dated. Possibly based on limited boxes being available at the time.
Sort of like how (I presume) it was lack of many boxes and ads being available at the time which allowed the name "Special" to get stuck to three-color corks.
Part of the info I'll be trying to gather together from George will be his conclusions about Hero and Unique being later names for Royals and some other patch. I should have gone to find it before I posted, but I often do things backward. Make the post and then it gives me the incentive to hunt for the extra info.
Now you've got me wondering about the birds. When where they made? In the texts from back when, I seem to recall Heroes and Uniques being thought of as "early". But I tend to agree with George about them being later. Some evidence for them being later is the names showing up in a later Master advertisement ... which I will now scan.