Glen,
Good reasoning.
In looking closely, the threaded hole on the front of the pan on the driver's side, sits slightly higher than the drain plug hole ... must be for the 'sludge factor'.
I actually decided to just ask Aviaid, short answer is:
- The hole on front of the pan (driver's side) is for the
oil temp sending unit
- The hole in the upper portion of the sump, on the passenger's side is for a dipstick tube.
So there it is!