RVDT sez:
The practice of cranking with the MAG switch in the OFF switch and then switching to BOTH (while still cranking) would probably instigate physical violence from most engineers witnessing the event.
Yet that's exactly how we used to crank 47's. (And yes, I am that old too.)
Why is this objectionable to engineers/mechanics? In retrospect, I can't really think of a good reason to do it that way, other than to get some fuel into the cylinders prior to adding the spark.