The Lubavitcher Rebbe ZYA was NOT a posek. When he spoke about wine vs mashke, he was rightfully concerned because Chabad was expanding far and wide, physically and socially outside its old base of Russian chassidim in NY, EY and Paris, and newcomers could have various issues with kiddush on mashke.
He deferred to a community rov for simpler shylas and to Rav Moshe Feinstein for complex issues. The only real psak halacha the Rebbe was involved with had to do with ships traveling on Shabbos, and he was consulted davka because of his engineering knowledge.