Actually, that's not right...as it supposedly is of Atari's
Video Chess. Programmer Warren Robinett already had the idea of attempting an interpreter on the machine before Atari started looking for cartridge games to utilize the keyboard controllers - to make their purchase more appealing to the public...and subsequently (potentially) boost sales of keyboard-controlled games already in the catalog.
BASIC Programming was a perfect candidate. Programmers in those early days were not under any kind of schedule to begin or complete a project. Regardless of how limited the resources are for the interpreter, it's still a pretty good achievement for the time.
http://toadstool.net/games/adventure/interview4.htm