The "tool use" everyone talks about with ISTPs can extend to intellectual tools too, I think.
Him: Problem -> What tools do I have to solve this? -> Destroy problem
Me: Problem -> What does this problem imply? -> Model those implications -> Reduce problem to special case of the model
Does that sound like you at all?
His SP nature is more apparent in other areas (skydiving, etc) but I chose this after all those S vs. N intelligence discussions lately.
my approach to things is to grasp the underlying mechanics and manipulate them to whatever ends i want. i have a natural aptitude for mentally "disassembling" things. your friend's approach seems similar, due to his understanding of the problem he was able to ignore parts of it and manipulate others into an answer.
for instance, in my highschool math classes i would often disassemble the equations learned in a given chapter then integrate the pieces into a calculator program so that I (and, unavoidably, a lot of the other students) could enter the known variables found on that chapter's test and get the answer.
id say my ability to understand and manipulate mechanics is more of a defining characteristic than my use of tools, although that is something i often do. "tools", to me, are anything that allows me to leverage the mechanics of something, whether that is a thought process or a socket wrench.
ingenuity is something i highly prize
speaking of skydiving, i plan on doing it
as well as base jumping (and those awesome wingsuits!)