The point is that up until now, humans were the best at these competitions, just like horses were the best at racing up until cars came around.
The other commenter is pointing out how ridiculous it would be for someone to downplay the performance of cars because they did it differently from horses. It doesn't matter if they did it using different methods, that fact that the final outcome was better had world-changing ramifications.
The same applies here. Downplaying AI because it has different strengths or plays by different rules is foolish, because that doesn't matter in the real world. People will choose the option that that leads to the better/faster/cheaper outcome, and that option is quickly becoming AI instead of humans - just like cars quickly became the preferred option over horses. And that is crazy to think about.
I feel the main difference is cars can't compress time in the way an array of computers can. I could win this competition with an infinitely parallel array of random characters typed by infinite monkeys on infinite typewriters instantly since one of them would be perfectly right given infinite submissions. When I make my tweet I would pick a single monkey cus I need infinite money to feed my infinite workforce and that's more impressive clearly.
Now obviously it's more impressive as they don't have infinite compute and had finite time but the car only has one entry in each race unless we start getting into some anime ass shit with divergent timelines and one of the cars (and some lesser amount of horses) finishing instantly.
To your last point we don't know that this was cheaper since they don't disclose the cost. I would blindly guess a mechanical turk for the same cost would outperform at least today.