In fact, I think in the well-meaning drive for a head start, we often even counterproductively short-circuit even the way we learn new material, at a fundamental level.
In this case, however, " to steal (someone's) thunder" means to take attention away from someone else, or to get the praise of other people before the other person can.
Pushing against these scientific arguments, however, is the perception that a zipper merge allows late-merging drivers to steal a march on those who have dutifully merged early to reduce hassles.
AP, IB, and dual-enrollment courses can have additional fees, but they're great opportunities to earn college credits for a lot less money before you even start college, which gives you a head start.