I think it wasn't just the final one.
The rules made it sound like ALL of them were time stamped. From the time you opened the puzzle until you clicked "Submit" to save your final results, there was a time clock running. The 10,000 finalists were the ones who completed all the puzzles and then completed the final process to submit the "Final Completion Form" and the "Contest Entry Form" the fastest.
I completed all the puzzles, but every time I started, I got interupted by something going on in my house. So, I was not surprised to not be a fianlist.
Congratulations and good luck to everyone who is a finalist.