Comment # 2 on bug 1124544 from Wolfgang Bauer

I suppose you mean "the screen is not locked when coming back from suspend"?
That's different from "automatically logs in"...

Or do you suspend from the login screen (e.g. sddm)?

(In reply to David Seward from comment #1)
> I should have mentioned that KDE was never told nor set up to automatically
> login on start up.

That's the default on a fresh installation though.
But has nothing to do with the screen locker, nor suspend/resume.