The [Previous Lubavitcher Rebbe writes](http://www.chabad.org/library/article_cdo/aid/81914/jewish/Preparations-for-the-Debate.htm) that the Shabbos before the great debate in Minsk, the Alter Rebbe served as the chazzan and baal koreh for his minyan. Furthermore, although the Alter Rebbe used Ashkenazi pronunciation, he did differentiate between Ches and Chaf, and Ayin and Aleph, like Sephardim.

Why doesn't Chabad read like this now? Did the most recent Lubavitcher Rebbe's baal koreh read like this?