Not a printing flaw.
The blank back "cards" are the front-cards for the retail blister/hangar packs. These are thinner than the regular cards and have the same front as the base cards they represent.
The construction is a cardboard hanger pack with a plastic insert (making the packs difficult to open). Inside the bubble is a blank white pack with the "face card" which is just a thin gloss/paper card with the card front art and blank back. I cannot find a picture of what the hockey packs look like, but here is a picture of what it looks like for the baseball release:
https://i.ebayimg.com/images/g/v44AAOSwl4xerwXa/s-l1600.jpg
Presumably, the baseball packs also will have the same facing card (thin stock/ blank back) but I have never opened those, only the hockey ones.
Also, IDK about a checklist, but there is not a card for each in the base set. I have not seen any parallels used for the face card. There might be 10-20 of them in total (again, for hockey as I can't speak about baseball or any other sports).
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