There is nothing dishonest about paying off a loan in one month. It's all fair in the contract.
I once got a long-term mortgage and paid it off in full within two months. The contract of course allowed me to do this without penalty. But in this case I told the underwriter that I would be doing exactly this. They were still happy to underwrite my loan.
Personally, I would rather tell the lender the truth in this instance. If they don't want my business as a result, then I want to know this information, because it affects my purchasing decision.