"Locked" means to fully extend your forearm, until you run out of room for range of motion.
This is "LOCKED" or max range of motion, to unbend the elbow. "LOCKED" does not always mean the bow arm will be in a straight level line. So, this is an extreme case of hyper-mobile elbow, meaning the bow arm can go, can bend beyond "straight", goes past "straight". Just line up the upper arm bone with the forearm bones (two in the forearm). If your arrow is level at full draw, then, try to LIFT and RAISE the elbow joint up to the same height, as your shoulder joint. If your elbow joint is LOWER than your shoulder joint, if the elbow joint is CLOSER to the ground, than your shoulder joint, UNBEND your elbow some more.
IS this fellow's elbow LOCKED? Probably not. So, does this guy BEND his elbow some, a little, a skosh, a tad, a bit, a little bit, MORE than a little bit, MORE than a skosh? Just get the bow arm level, when your arrow is level. Shoot some arrows. Do you like the results? Then, bend your elbow 1 degree more. Shoot some arrows. Do you like the results NOW? Play with the FEEL of your bow arm, and see what you can repeat shot after shot after shot. When you find a full draw posture that works for YOU...then, you are done. cuz, that is what matters. What full draw posture allows YOU to get results. Not what some other guy does. Find what gives YOU results, the results you are looking for.