This name is a synonym of Rhododendron cinnabarinum subsp. tamaense (Davidian) Cullen.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50280259) with original publication details: Rhododendrons Magnolias Camellias 1972: 54 1972.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:333444-1.
This name was in version 1 of The Plant List, record tro-50280259, and has not been changed.