From the post:

> The fountain is required for wishes. The wall is required to be able to offset the random state without advancing the game state – every time the character attempts to walk into a wall, it calls random() without wasting any in-game time. From the fountain, the bot ascends completely on her own.

They describe that in the article. To be able to bump into the wall and advance the RNG one step at a time without passing in-game time. Presumably that's to ensure that the next Wish will be successful.