You are all misreading the letter. Read the first part where he defines “meshichistim”. Meshichistim= dead rebbe. Notice that he explains in his meshichistim section how once someone dies they’re not moshiach. Elokistim = living Rebbe. Shlita goes with yechi, a declaration of kefira. Notice how he says meshichists are crazy for believing the messiah will come back from the dead. Living people don’t come back from the dead. Not sure who yechiniks say is buried in the Rebbe’s ohel. Even his hanacha to the dead moshiach folks says if they’re not apikorsim, it’s assur to be mechazeik them
Years ago Rabbi Krinsky put up a plaque referring to the Rebbe ZT”L. It got torn down.