It's not the first case of a game with a patterned bottom.
https://www.ipdb.org/showpic.pl?id=856&picno=66834
Some classic stern games have a brick pattern
https://www.ipdb.org/showpic.pl?id=2089&picno=53443
It was likely used because it was probably cheap material that may have been a cast-off/reject, they weren't able to get enough of the regular material fast enough, and/or a combination of both.