> From a human perspective, it's not apparent why, as a large part of the solution is very repetitive. It feels as if there should be a more condensed representation for iterating over problems like that one.

I'm not sure how 'in' you are, you might know this already, but for sokoban IIRC the recommended way is to treat things is topologically - you always do a flood-fill empty space from the player so that the decision isn't whether to go up/down/left/right on this turn but which accessible side of which crate to push. It decomposes quite well, and maybe makes the complexity a bit more obvious? Hmm...

I haven't looked into mazebench, but yes this is very related stuff.