the Rebbe is talking about “betten” in English, “asking, demanding, beseeching”, something Chassidim have done throughout the generations, and across the Chassidish spectrum, it’s not exclusive to Lubavitch. In Yiddish we say about someone who has passed on, “Er zol Zayn ah gutte better”
Nice try, but the “Er zol Zayn ah gutte better” means the neshomo is beseaching Hashem, not that we’re beseaching a neshomo, ch”v.
If all the Rebbe was addressing is how you can ask a Rebbe to daven to Hashem, well, nobody really questions that (you can ask anyone to daven to Hashem for you), and the whole atzmus umahus areingeshtelt in a guf bit is unnecessary.