defacto I advise you to check B737 FCOM Performance Inflight section rather than your "source", because in accordance with official manual of B737 if a runway is wet, it is defined as "Slippery" it also includes performance data for good-medium-poor braking condition. Beside I didn't ask what is wet or dry. I've just asked a specific performance question about a certain condition. If you have answer I will be glad if you share if not please do not interfere the subject with irrelevant information.