Thanks for editing the original post with the conclusion.
Also, it takes a lot to change one’s mind, so kudos to you for doing so.
is the competition you mentioned still active?
I’ve found a method that reduces the 2⁷⁰ search space of Puzzle 71 by approximately 7.22%, without using any prefixes or hash tricks. I've tested it in Python.
I just hope the competition is still ongoing and the reward is valid. Once I wrap up some other work, I’ll share the method.