I found several online references to a M. le commandant Loste who commanded franc-tireurs fighting along the Lyon route in the Franco-Prussian War in 1870*. I also found a few references to a M. Lucien Lhoste who was elected to the board of the Rose section of the Société Nationale d'Horticulture de France about 40-45 years later. Also serving on the board was one of the authors of the 'Nomenclature' book, Charles Cochet-Cochet.

M. Lhoste may or may not have been related to the commandant Loste; it wouldn't be the first case of spelling inconsistencies with family names, but I wonder if the spelling (or mis-spelling) of the rose name in the 'Nomenclature' book may have been influenced by Cochet-Cochet's acquaintance with M. Lhoste? That is the only contemporary source that I could find with that spelling.

In Cochet-Cochet's Journal des Roses, the reference to the rose is as 'Commandant Loste' and dates from 1906, the same year as the book. My guess is that 'Loste' is the correct spelling; 'Lhoste' may have been a typo or an alternate spelling.

Should we treat 'Commandant Loste' and Commandant 'Lhoste' as synonyms?

Virginia

* From 'Chronique Scientifique' 1870: "Les compagnies de francs-tireurs qui ont repoussé l'attaque tentée par les Prussiens à Saint-Jean-de-Losne sont la deuxième compagnie des éclaireurs du Rhône, capitaine Cléinencet; la première compagnie de Vaucluse, capitaine Fabry, et la compagnie des volontaires d'Alger, capitaine Landcemann.
Ces trois compagnies étaient commandées par le commandant Loste, notre compatriote.
Ce sont encore ces mêmes compagnies qui avaient participé à l'affaire de Calinoutiers."

Also: https://fr.wikipedia.org/wiki/Armée_des_Vosges_(1870)