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I don't get it either. The only thing behind that threaded hole at the rear of the crankcase is oil. It would go straight into the sump.
This image is of a 900SS but it is essentially the same.

In a very close position there's the bypass valve for extreme pressure (spare part manual 066049020 tav 11 #17). It's in the other side of the case but there might be some unwritten modify