I did check that possibility here. Can't see that passage on the extant assembled machine but I can see it on the drawings. That drain hole looks to me to be inaccessable without moving the spindle at least an inch or two to the right. There is NO way to get in there with a bent tube from inside the headstock; big gear in the way. That gear is now loose and slides freely, but not far before it hits a projection in the headstock casting.
Perhaps a dentist crosstrained as a proctologist (or vicey versey) who can do rear-entry root canals could do this ...
How did you do that without moving the spindle?