Is a misah meshuneh any death not from natural causes? Or perhaps only a painful death? I’m not sure how much you can be medayek, but in R Chaim Kanievsky’s letter to the Yifrach, Frankel, and Shaar families, he uses the term “misah meshuneh al kiddush Hashem”. If every instance of being killed al kiddush Hashem was a misah meshuneh, those words would be superfluous.
Your examples of a hypothetical reprieve for R’ Akiva, Chananya Mishoel and Azarya, and Daniel, are all poor examples, since the alternative would be continuing to live, but that wasn’t the discussion.