Sorry for the delayed response, my computer was down for a few days.
Anyway- this plug is not the sump plug. I have done my oil changes a number of times and your right you really need to change the alloy washer each time to stay 100% dry. This plug is a allen socket head plug that faces forward (like the sump plug)above the sump plug. it sits between but forward of the two center main bolts. I have a 2005 speedmaster for reference.
I'm thinking it is one of those holes made to drill an internal oil passage then was plugged with this said plug(???).
Gary
