This name is a synonym of Allium subhirsutum L..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 464952) with original publication details: Index Kew Suppl. 4: 8 1913.
This name record (from WCSP) 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 Allium loiseleurii in version 1 of The Plant List.