Julie - we've had this situation come up one way or another at our bank a number of times. I certainly think you could argue either way, but we would not report the loan you described. The funds are to improve the same dirt the house sits on but the improvement is for business purpose, not improving a residential property directly (home, in-ground pool etc).
We have taken a similar question to our regulators: a loan to a farmer to put drainage tile in the ground on his 80 acre farm and build a machine shed to store his farm equipment (improving the farm - business purpose). We have the farm as collateral and there is a dwelling on the farm. Our regulators (FRB) agreed, not HMDA reportable as improvement due to the mixed-use property exception and advised us to have supporting documentation in the file.