I don't think it necessarily adds an unneeded level of complexity. A level of complexity, yes. Unneeded, I'm not so sure.
The only thing they care about, at the end of the day, is how many gems people are buying. If they can implement some complex scheme that results in people spending more gems, they will do so. Many people have observed that the drops seem to be unusually "streakish" in this game. I've observed it myself, and I have a master's degree in Math, so I know what randomness looks like, I know about the observer effect, etc. I've played a lot of online games that people have superstitions about how to beat the RNG in, and in all those games I'm not convinced that it's anything other than a standard linear congruential generator, or similar. In this particular game, I'm not as convinced.
When you've got a million, or 5 million, or some other large population, it's very easy to run A/B tests on this population and measure the effects of different things. The results are not always intuitive. I've experienced this firsthand. I've actually seen real numbers from a real game of how changing certain variables in subtle ways changes the spending habits of the population.
So not only would it not surprise me if they were doing something like this, it would surprise me very much if they were not at least experimenting with it.