Well this is interesting. I don't own Kindercomp....but I own a couple of other Spinnaker carts. I actually have TWO copies of Alphabet Zoo, and they have two different shell types! (PS - one of these is now for sale/trade in my store). Note the grip strips on the back of the top row.
I also included MasterType, which is a different company completely, yet uses the same cart shell as one of the Spinnaker games.
None of mine has a loose label, so I can't open them up too see if an EEPROM is present.
My best guess is that some of the minor 3rd party software houses farmed out the manufacture of their carts to whoever was cheapest, and that could change over a production run. That EEPROM board you found may just be a prototype/proof for a new cart production run. They didn't waste anything...just throw that test cart into the run....