The real problem is that, because we tend to think in a linear fashion, people try to do the puzzles in order. While there are some puzzle dependencies, the puzzles are rarely completed in exact "numerical order." In fact, the puzzles aren't even numbered in the game, despite the fact that they are referred to numerically in the discussions of them. The truth is that the 12th puzzle can be solved much earlier in the game. Most people don't realize that because it's somewhat of an easter egg that has to be worked at to find.
In addition, there will be a permanent place to train builders when the v1.1 update is released (just in case people wait to the end to solve that last puzzle).
