From my experience (not hypothetical) warpage can take place whenever the metal is heated above the "critical temperature". I've seen it in old metal that was pre-anealed and in metal that had never been hardened. I'm talking double shotgun and single shot rifle actions, lockplates, trigger plates, forend irons, triggers etc.
Casehardening without the likelyhood and readyness to "hard-fit" after the fact is wishful thinking. Many jobs don't require it, but you had better be ready for some serious "tweaking" if warpage occurs. Straightening is not recommended for the inexperienced or heavy handed. The "hard-fitter" was once a job title for maker's of new guns.