On modern PCs it actually uses the CPU's internal performance counter. I've heard of some cases when QPC() returned zero (i.e. failed) due to some hardware issues.
But you're right, it's not a big deal to try QPC() and fall back to GTC() should it fail. Khaled may have used GTC() because it was supported both on Win 3.1 and Win 95 (just a guess).
