Same. It ought to be there for a reason. Some more digging and poking around is in order.
And, again the lines that go vertical then horizontal part way up the wall, group together are the vent stack lines, ensuring proper drainage and flow of the waste lines, by letting air in from the roof area. They possibly tie in somewhere with the bigger main stack.
Maybe through the realtor, or directly, reach out to the previous owner, to ask about the purpose of the hole, how, what, why, ... what the intention was?
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