A passive bias is triggered when a bias signal’s probe has not been maintained when the bias window opens. This is labeled “Reverse bias”, because having held a test of one bias signal puts into plan an offsetting test of its counterpart, the opposite bias signal.
Meanwhile, this bias window is also “No-bias”, so its range should be contained between its bias signals. Probing either signal should hold that signal’s test. Probing prematurely beyond either signal could require retracing back to the signal that was probed prematurely.