This name is a synonym of Phlox drummondii subsp. tharpii (Whitehouse) Wherry.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50229547) with original publication details: Genus Phlox 62 1955.
This name was in version 1 of The Plant List, record tro-50229547, and has not been changed.