guess they planned on the trans leaking oil and did not want it to get on the clutch plate so they installed a bit of insurance, a drain hole.
my trans TO=35 has leaked oil out of the drain hole for years, but no clutch problems as the weep hole has a upside down carter key installed.
As the tractor travels through weeds and grass the key turns and keeps the hole open.
Note to file: if you ever get the tractor stuck and mud gets into the drain hole and stops it up and if your trans does leak, oil will build up in the reservoir and will get on the clutch pad.
i just keep the trans filled to about the halfway full mark (lift arms must be in the down position when you check the fluid).
you need the maximum amount of fluid in the reservoir and not stored in the lift cylinder when checking the fluid level.
Again, ask some older fergy repairman about those brass, bronze bushings in the older Fergy transmissions and what oil is best lube for them. gl-1
New tractors do not have those type bushings bearings in there transmissions.