The type of dog he's describing certainly sounds like an LGD in every way. Since he says the dirty white colour I would think most probably some relative of the akbash. That classic white LGD was all over eurasia, and just certain strains got made into "breeds" here and there. Maremmas, akbash, pyranees, etc. These breeds got toned down a lot from the dog type they descend from and represent, so I'd suggest the dog he's describing is this white LGD type, the ancestor to the above family of breeds, which like I said spread all over eurasia. Just because there is no russian/siberian breed version(at least i don't think?) doesn't mean much to me, understanding how new and arbitrary the breed concept is.