> I've never really needed to do this because well what good would it do you really

ISTM it's not about avoiding triggering undesired behaviour, or "debugging" third-party code (as in finding bugs you don't own). It's about debugging your own code as invoked by third-party code - that's usually an underdocumented black box in application frameworks everywhere, where control pops in and out of your code from mysterious locations beneath the water. Figuring out the exact ordering constraints and implicit assumptions is tricky at the best of times when using trial and error; good luck trying to do that with documentation. Using the source (any readable representation of the source) is leaps and bounds ahead.