SHY: ” it’s not hard to imagine that on Sukkos he stayed up at night, as he often did during the week, and slept intermittently at other times”
That doesn’t exempt him from sleeping in a sukkah as even a shinas arai, as opposed to achilas arai, is mechuyav. And we all know how makpid lubavich is on eating or drinking anything in a sukkah, so according to basic halacha he should have gone to even great length to have naps in the sukkah.
Again, I’m not saying that the minhag of not sleeping in the sukkah is wrong, even though I don’t know where the minhag came from. I’m saying that the “lomdishe” excuse makes no sense at all.