Why does this option exist? In general, the mac default application is used. I was boggled (I wasted 20 minutes) by why some .rb files opened with one application and some opened with another (but only in FS)! Eventually I tracked down the difference to the executable bit (which still left me confused), and then stumbled upon the preference.
Hmm, maybe it would make sense to just defer to the system standard setting. I'll have to think about that. Sorry you ended up wasting time trying to figure it out.