The Bass Muff isn’t a re-issue as much as the voicing was “inspired by” the Russian muff. The Bass Muff, as a result, has a distinct sound when you compare them up close, although they are similar. As well, the Bass Muff’s tone pot is set for bass (while the Russian is technically a guitar pedal) and the Bass Muff also has the toggle missing from the Russian.
They are close but different. I’m a bassist and I jumped on the Russian re-issue!