goodbye: I refuse to reply in kind to your rude and obnoxious tone. I am surprised that the mods let your post through, which only goes to debunk the complaints of over moderation.
My Roshei Yeshiva were from Slabodka, Brisk and the Mir and all said the minhag was to learn on “nittel”. Same goes for my grandfather from Kovno. I don’t have access to Chok uZman, but I know it was written by a Belzer chossid, I trust those who grew up in Lita to know minhagei Lita more.