Did you even watch his radar lock? The target wasn’t even close to maintaining his notch through the engagement.
All that happened here was he maintained the DL+IOG through his targets notch and then when it left the missiles seeker was close enough to pick it up.
IOG will only get the missile close. If you are maneuvering in the notch and maintain it until the missile passes it will not get close enough. This is amplified if the shooter stays in TWS and cannot afford to STT as the IOG will not update as quickly.
This also only works when the shooter is under no pressure. If the target even just panic fires a return shot at max gimbal it will for the shooter to turn away themselves.