The regulations don't consider wet runways at all - Part 25 only deals with landing on a dry runway (25.125 refers)
The operational rega just set landing distance for wet based on dry runway perf with a factor (15%) and dry data has no TR, so the wet "planning" distance has no TRs. But it's a fictional distance anyway, because you'll need rather more than 15% more distance in wet/slippery in most cases.
IF the OEM chooses to supply wet distance data for guidance then it probably does include TRs - but it's not a regulatory distance, just manufacturer's data.