With the less-than-effective moisture sealing capabilities of spark plug and coil wire boots that was common in the 1950's and before, it was pretty common practice to have the coil output wire at least pointing downward, if not completely vertical. Any splash or condensation would drain away instead of providing a path for voltage flash over to the primary terminals. Chrysler Corp. engines mounted their coils at about a 45 degree downward angle, and up until 1949, most Ford coils had their high voltage terminals at the bottom of the coil housing. GM was probably just following the accepted industry practice. If a coil leaked oil, it got replaced.
Jerry
