I answered "no" only because I don't have any. I intend to get several in different sizes, if I can, to fit each of my flintlocks, but haven't gotten around to measuring them all yet.
While that statement is a gold standard for manual of arms safety, there are some guns that ONLY have half-cock and nothing else. I always test half-cock before loading by both pressing the trigger and pushing on the hammer (or the cock, as applicable to lock type).....
Also, one should NEVER rely solely on the half cock notch, on ANY gun.