StarFox was one of the biggest game launches Nintendo did up to that point, and I imagine they were making copies of that using any and all cart shells they had left in their inventory.

BTW, both my StarFox and Super StarFox Weekend carts have the new style shells. My StarFox PCB has a date stamp of 9324 (Early June) and my Super StarFox Weekend has a stamp of 9312 (late March).

Also, the Super FX coprocessor has never been pirated, so the chance of the game being pirated is non-existent.