Exactly! O'Kane is the closest approximation we can get to the flexibility of the U-Boat attack at 90º to the target track. With it you can accurately shoot at any time before or after the only valid aiming bearing for a chart attack. This flexibility leads to more shots taken, therefore it leads to more hits per patrol. A shot not taken never hits its mark.
Remember that the Dick O'Kane instructional video is a BLOWN ATTACK. I was busily running my big mouth as the target blew past the aiming bearing. No matter! Without even updating the AoB (because there just wasn't any time) I just aimed up the zero bearing, pressed send range/bearing and shot anyway. Because the TDC automatically calculated the correct new lead angle, which was no longer 9º, I still sunk my target, salvaging both the attack and the video.