I guess at that point, if he signed a business purpose statement and that's what he said he was doing, then I'd treat it as such.
I don't put a lot of stock in a business purpose statement. Dealt with too many loan officers over the years that as a matter of practice always had that statement signed.
If the bank has knowledge the borrower is using the money to purchase a primary residence and the loan officer has the borrower sign a business purpose statement to avoid consumer disclosures that is both, IMO, evasion and fraud. The fraud portion would require a SAR.
The opinions expressed are mine and they are not to be taken as legal advice.