The space is large, it just turns out if you direct Mario to explore with a bit of bias (so, in general, there's some favoring of exploring from states where Mario's x coordinate is to the right, e.g.) it completes the levels.
I think Pokemon could be beaten with our techniques. Final Fantasy on NES poses similar problems to Pokemon, and that is a game at which some progress has been made in the past, here.
There's no learning exactly, as the post explains the fuzzer is aware of various RAM addresses (as well as having a tactic for how it "presses" buttons in the game). It's just trying to explore the space of Mario's level + his x and y coordinates.
March became the new year again throughout much of the West in the Middle Ages as it moved to the feast of the Annunciation. March 25th was New Year's Day in England until the Gregorian calendar was adopted in the 1750s!