Nice article - but the BBC did get a major detail wrong. The mazes are not always solvable - Figure 5 in the paper (https://arxiv.org/abs/1811.02035) explicitly demonstrates an unsolvable maze sample from the game, which can only be solved by collecting and using a "make-break" powerup (which allows the user to create or remove a wall).

They interviewed a co-creator who claimed it did always make solvable mazes, which is probably where the BBC journalist got confused.