DY: “Lack of any other hot food is tzorech gadol, that was actually Health’s case on which this discussion began”
But the Rema says no such thing. He never says they had no other food!
“I’m suggesting a reason that the R’ma does not allow cooking even l’tzorech gadol. If you have a better reason, kol hakavod, but clearly he assers it”
But he does NOT mention any problem with cooking when there is a Tzorech Gadol, so there is no need for a “better reason”.