@Sviatogor who can understand that study, I have no idea what those trees are saying. Lexical relationship isn’t the only thing that makes language close, grammar, and phonetics are important. French and Italian are lexically closer to each other than Spanish and Italian yet an Italian would understand more and feel more comfortable with Spanish.
Slovak is lexically just as close to Ukrainian here as polish, and rusyn an east slavic language is closest to slovak. Russian is suprisingly slightly closer to Polish lexically than to slovak. Again lexic closeness doesnt mean over all language closeness, but a broad statment like polish is closer to eastern slavic languages is misleading.