The report hints at the reason,
FAA SAFO 15009 explains: Purpose: This SAFO warns airplane operators and pilots that the
advisory data for wet runway landings may not provide a safe stopping margin under all conditions.
In a nutshell, the FAA SAFO are saying wet runway landing distance including factoring isn't sufficient to cover you behind. A training Captain once mused to me about a hypothetical exchange between a prosecutor and a Captain in the subsequent court of inquiry:
"So Captain, was the runway wet or dry"
"the runway was damp, therefore the manual says it could be therefore considered dry"
"Captain, If you sat on the runway, would your bottom be wet? No further questions your Honor"