the concept of the shechina resting in a tzaddik just like in the beis hamikdosh is found in nefesh hachaim (my favorite litvishe Sefer). See nefesh hachaim 1:4 in the hago I quote
לזאת הרי כי ודאי עיקר ענין הקדש והמקדש ושריית שכינתו ית’ הוא האדם שאם יתקדש עצמו כראוי בקיום המצות כולן שהם תלויין ג”כ בשורשן העליון אז הוא עצמו המקדש ממש *ובתוכו* ה’ ית”ש
By that logic one can daven TO the beis hamikdash. As far as I know, Lubavitch doesn’t advocate for that. It’s one thing to daven towards it or to have the makom Hamikdash in mind, but not to daven to the building Chas veshalom.
Therefore it is clear to me that this is a misappropriation of the teaching of the Nefesh Hachaim, and him saying the shechina rests in a tzaddik clearly doesn’t include permission to daven to him.