N0m: You’re going in circles. You’re misapplying “Ain dochen nefesh mipnei nefesh.” A) You’re using it to claim that the Halacha (and it is undisputed that it is Halacha as I cited above from numerous Halachic sources) in Horayos doesn’t apply. How can you claim to erase Horayos? How can you disregard the Halacha from Horayos?
And B) Ain dochen nefesh mipnei nefesh isn’t applicable since the crew, by mathematical fact, MUST choose who are the few that can be saved, since there isn’t enough to save all. Each individual passenger has no claim to a seat in the still unoccupied lifeboats. The crew has the right to decide who can enter. (Otherwise they’ll be chaos and everyone will sink.) Just as an Emergency Room with insufficient space must choose who to admit. You can’t just walk into the hospital and jump into an unused hospital bed and yell Ain dochen nefesh mipnei nefesh.
That’s why Horayos comes in and determines the triage order.