Travis, your question is a fair one, but it's too fuzzy to answer definitely as cold, hard fact. Also, January isn't enough sample data for that specific of a question, but let's try anyway:
If we evaluate the prize puzzle as a separate round, and only look at round three for the rest of its value, what happens to the numbers? Actually, they look like this:
Rd 1: 11 / 23 (48%)
Rd 2: 11 / 23 (48%)
Rd 3: 10 / 23 (43%)
Prize: 9 / 23 (39%)
Rd 4: 9 / 23 (39%)
Rd 5: 3 / 4 (75%)
Of the 23 games in January, 9 of them were decided by the prize puzzle. (It was a quick glance, so +/- 1; but let's go with it.) That means that the prize puzzle was, by itself, worth about an entire round. Again, January by itself isn't enough data here. But to put things into perspective, the big final segment that's supposed to decide the game? The winner of that round also runs 9 / 23.
So picture a game of Family Feud where the values of the boards progress S/S/D/S. That's not too far removed from what we have here.
But the true effect of the prize puzzle is going to be slightly higher, again because players in Rd 3 have less risk aversion than players in other rounds. So it's not just what the players do that affects the game, but what the players don't do.
To address one of your other points, three of the 23 games were won by someone who won only one round. Guess which one?