Miller et al. 2020 found G. montana to be a western North American taxon distinct from G. korfii of eastern North America and the European taxon G. gigas which does not occur in North America.
Not sure we can say that western montane species don’t usually show up in New York as Pluteus americanus is documented from montane Az for example.
However the 6 base pair difference in LSU indicates that ITS probably has even more differences than that. Western montane species don’t usually show up in New York. More gene regions need to be checked from more specimens.
Not synonymous with G. korfii
found it to be nested within G. korfii in the most recent phylogenetic analysis of Gyromitra that I know of. They’re possibly both synonyms of G. gigas but they weren’t able to determine that. I know that’s not set in stone, but unless you can find a more recent study that contradicts that this should stay deprecated.
This montane species is not the same as G. korfii – it is close though.