This name is a synonym of Hyparrhenia niariensis var. macrarrhena (Hack.) Clayton.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 419793) with original publication details: Fl. Trop. Afr. 9: 355 1918.
This name was in version 1 of The Plant List, record kew-419793, and has not been changed.