To anecdotally confirm this point: I am not a native Russian speaker, but I am fluent and Russian, and I am also very familiar with Polish (it's complicated). T

To anecdotally confirm this point: I am not a native Russian speaker, but I am fluent and Russian, and I am also very familiar with Polish (it's complicated). Those texts are very readable to me, so knowing Russian and Polish is likely to cover the widest base.