As shown in the attached extract from AC25-7A, the FAA's Flight test Guide for Part 25 certification, presentation of data outside the +/-2% slope band requires additional work by the OEM. Unless they need to do that for a (significant) sale, they won't.
OK, that didn't work
You'll have to take my word for it, then!
Or check the AC, it's in chapter 8 of the Ac (Airworthiness), section 230.