Are you skimming the clockwork levels?

Just to comment on your last point, the only time I've gotten lockboxes consistently was when I had silver keys from promo packs and was actually opening boxes. 1 box opened gave me another box in the prize wheel right after the opening took place.

Two things.

1) This is a huge pet peeve of mine: You mean "hypothesis," not "theory." It's a common mistake. A theory is something that has been tested thoroughly and found to be true. A hypothesis is a proposed explanation for a phenomenon. According to the American Association for the Advancement of Science - "A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact."

2) This would require a massive amount of data collection and statistical analysis to determine if it's true. Or, much more easily, a look at the game's source code, or a word from the developers themselves, both of which are not likely to happen. It's more than likely simple randomness and correlation, rather than causation, however. A simple random chance would require calling up one random number to determine the wheel's prize. Changing the prize based on performance would require gathering all sorts of figures about the player's time in the level, then getting a weighted random number based on all those figures. Pure random chance is easier than weighted chances.