A mechanic can pull an engine through and by feel know that it is normal or otherwise. A pilot usually does not have that experience or ability. I never pulled the P&W 1830s through because they had an inertial starter that did that for me. The P&W 985 I do pull through because the manufacturer says to do it, even if the engine has a separate starter (not included on the ignition switch). It always feels wrong to start those engines that have been modified with a Cessna-type start switch.