Ah, that makes sense, but I'm still seeing inconsistent behaviour in how that's applied, which stopped me from getting a feel for what it was doing.
Testing it outside of opening moves, if I push the first block down and walk around it to push the second block down, and then hit Z after one push of that second block, the game will sometimes rewind my last single push, and sometimes wind back two pushes (to where I'm about to push the first block a second time). If it's making a clever call about grouping less interesting pushes together and skipping them all, it's applying that inconsistently.