Heat will go up, wherever it can. Venting heat over the plastic of the headlamps makes no sense. Heat cycling plastics means the plastic will crack/degrade sooner.In my opinion, Toyota intentionally left that gap unsealed. The hood gap over the headlights, while unsightly... appears to function for heat extraction. If you hold your hand across the gap area after driving the vehicle, the heat escaping through the gap from the engine bay will be detectable. Significant heat extraction is not detectable elsewhere, not to the rear of the hood, the front grills or under the vehicle due to the aero cladding that covers most of the engine bay. In my experience, water intrusion through the gaps due to rain or car washing has been minimal.