I’ve noticed that they are somehow identifying when this method is used now. When the puzzle completes, you no longer get the success message – ouch! I’m guessing that they keep track of what percentage of the pieces are put together in this linear order. I’ve verified it even with this small puzzle to test. I tried a real one and even mixing up a handful of pieces and waiting a reasonable time to complete it didn’t give me success message (but I get one fine if i do it by hand). https://www.jigidi.com/jigsaw-puzzle/sd32gq5t/easy-9-piece-geocaching-test-puzzle-with-completion-message/