Who's trying to prove the Goldbach conjecture before they learn the rules of algebra? Most kids in middle to high school math classes aren't worried about their "mathematical maturity" or about having powerful insight. Rather, this obviously shows that the rules of algebra can be applied to other sets of symbols, and that letters and numbers are simply a subset of a much larger set. How is that not a powerful notion? If you're bothered by this, then go back and read Herstein, or any other intro to group theory. Seriously, this is a great way to get kids actively thinking about the rules of manipulation of symbols.

The seeds of abstraction must be planted before you can play with more lofty ideas. If games aren't a good way to enjoy mathematics, then you have missed the point of a lot of math.