> Sorry, I don't understand: what frames?  We are talking about
> non-interactive situations, no?

There's nothing non-interactive in the OP use case. And desktop.el already contains

Try

  emacs -Q --batch --eval "(progn (desktop-save-mode 1) (kill-emacs))"

so what I'm discussing is whether desktop.el should try to protect the desktop when the user, or some code, runs `kill-emacs'.

> Why?  In "emacs -Q", the desktop you have is ephemeral

Obviously, I'm not talking about the -Q case, and I don't thing the OP is, either. That's just a recipe to show that kill-emacs asks an interactive question.