Adams was fully focused.
As a safety, positioned slightly to the back, he could see everything in front of him clearly. He had all movements under control and noticed Li Wei and Hertz's exaggerated "fake run and real pass" performance immediately, and then he saw Hertz leave the pocket.
Shock!
Generally, a quarterback wouldn't leave the pocket, for without the protection of the offensive line, he becomes extremely vulnerable, totally exposed to the defense; mobile quarterbacks, however, are an exception. When they leave the pocket, their field of vision opens up, and the dual threat of passing and running kicks in fully.
However, Hertz did not choose the read option, yet he still left the pocket, which meant—
His gaze quickly swept the field.
Li Wei!
Hertz and Li Wei split up, each making a dash as if to run.
The double running back tactic, Crimson Tide Storm actually employed this strategy again, using Hertz as a second running back in such a critical moment.