>The hopefully part is where thread-state becomes unpleasant, because if you want to do concurrent work, you must pass one thread's state to the other. The other thread has no guarantee that it is there, so the programmer must either hope it is or verify it, which is annoying.

Right, so then you are in a situation where you can always rely on it implicitly, until you can't.

Much better to be consistent and force the inclusion everywhere as you mention in your second paragraph.