The problem has to do with how the Trouble contributes to the 4PT.
If you’ve been using Combat the whole game, and you’ve increased Combat to (say) 60, and you’ve been neglecting your other stats, then you decide that being Stealthy is the better bet for this choice. But because the author wants there to be a “challenge,” the difficulty at this point in the game is something like a 55, meaning…you’ve had to specialize in a skill in order to be high enough to pass the test at this point. The player learns to just pick their best skill (the 4PT), and that’s the Trouble.
There are a variety of ways to mitigate the Trouble, and you can just not indulge it by spacing out the stat increases and not setting the difficulty too high and a variety of other ways. But it’s an problem inherent to unidirectional FairMath (in particular) variables.