Indeed. And sometimes it threw up some real gremlins, which highlighted serious lack of appreciation of energy, and therefore training. I didn't know the answer at the time, but that was not important: I watched PF RHS sitting idly by in VNAV-PTH, on the pipper, on speed. I suggested they look at PROG 1 and distance to TDZ and then the altimeter and consider if all was well. "But we are in VNAV PTH." so what can be wrong. I pointed out the discrepancy and we decided what was the best course of action. That in itself was a small adventure. On the return sector we analysed the previous 'curiosity' and came up with a reason hidden in the FMC. The PF was astounded how this could happen. It all looked so good. But why were they not applying their own 'on-board computer'? Another lesson ticked off that should have been done in LT and continually since.