This name is a synonym of Linaria genistifolia subsp. sofiana (Velen.) Chater & D.A.Webb.
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Repert. Spec. Nov. Regni Veg. Beih. 30(2): 140 1929.
This name record (from WCSP (in review)) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Linaria concolor in version 1 of The Plant List.