I’ve seen it a few times before. I saw a Base Pikachu with the white line at the top once. And I have a Korean BW Pikachu with a small line at the bottom of the back of the card. I’ve also seen it a few times before on Base Set cards, usually at the back and/or bottom of the card instead of the sides, though.
Although the line on your Articuno is wider than you usually see. (Off-topic: This error also happens on Yu-Gi-Oh cards sometimes.)
Greetz,
Quuador