I’m not aware of a bison grass vodka from Russia. I quite like the Polish bison grass vodka (Żubrówka). Though perhaps that’s your point.. the Russian variant having notes of paint thinner?

The bison grass mostly adds coumarin as a flavor component, which is the same component that gives Tonka beans their main flavor (also the popular Waldmeister in Germany). Personally a fan of that Vodka, never found it tastes anything like grass. But maybe we talk about a different one, I only know the polish one from Zubrowka.