It looks like the game pages might be dropping the leading zero if a UPC has one. If you look at 007 here you'll see the UPC was submitted with the zero but it was dropped on the game's page:
http://vgcollect.com/item/324/history. However, I did find one that didn't do that so I don't know:
http://vgcollect.com/item/19054. Wasteland UPC was submitted last year whereas the 007 one was this year, so maybe something in the database coding changed?
I've also noticed a few odd UPCs that were entered without the first and last number, and had a space in the middle (##### #####). Most U.S. UPCs should be twelve digits, though I believe some old 80s products might not list those end digits. I've found Intellivision games tend to not have a UPC directly on the packaging so I'd guess they likely stuck a UPC sticker on the plastic wrap.