M. micrantha has long been used in the sense of the species also known as M. stricta
see the long list of sources at https://europlusmed.org/cdm_dataportal/taxon/62d088d9-2c85-436b-9327-9d8f7b150a6d

However M. micrantha Pall. ex Lehm. in the original sense of Lehmann (who is the author of the name, not Pallas, who did use it in the sense of M. stricta (!) but never validly published the name) likely does not refer to a member of the genus at all (as was shown by Hylander (1945))

M. micrantha and M. stricta here are doubtlessly used for the same taxon and need to be merged