Oil Filter Adapter & tiny hole

[TX7A]

I removed the (angled) oil filter adapter from the accessory case so I could install a 3/4" spacer. While cleaning the mounting surface of the adapter I noticed a very small hole (1/16" approx.) drilled into a slot located in the main cavity. The accessory case had a matching hole & the gaskets had a provision for "flow-through"....I'm guessing.

What is the purpose of the hole?

...and the reason I ask is that the 3/4" spacer that I just got from ECi does NOT have the hole. So if this is some sort of bleeder orifice...or whatever for flow-through, it isn't going to happen.

Thanks for any info on this.