Indeed I have flown a Mavic 2 in intense winds and it handles winds almost up to its max forward speed of 45MPH with great stability as long as you have battery to get home or land. Stabilization of the gimbal and camera is improved over anything else out there except for industrial/cinema drones, and combined with the vehicle stability is incredibly solid.
I saw no rule violations at all except maybe line of sight, which is a tough call. Below 400, not over people, etc. Brandon is said to be one of the best stringers out there and makes his living doing this from what I hear. He does fly part 107 commercial flights, has the right training, and I've heard might also possess a special use waiver that are very hard to get.
Line of sight is just that- no obstacles between you and the drone on a line. The rule does state you should have unaided visual contact with the craft, but also includes language about first person view and observers in visual range as an alternate. In practical use, for these small drones they can disappear after about just 200-300 yards in some lighting conditions. External nav lights can help really increase that and should be used if available. Practically speaking I don't think it is a blatant safety concern if your drone is momentarily too small and far to see as long as you know exactly where it is and have a clear line to that position, but the letter of the rule is a bit more strict and should be adhered to. For example you know it is over that large tree over there even if it is a speck hard to see or momentarily impossible to see. No aircraft should be below 500 feet away from airports except in emergency or rescue operations, and you would easily be able to force land the drone if you see one in the vicinity of the flight. I think the primary intent of the rule is that you know where not to fly as far as obstacles, people and other restrictions, won't lose control, etc.- hence the alternate allowance of first person view (goggles) with an additional observer doing visual tracking. The strict letter of the rule does indeed say you have to see the drone so even trees or small things in your way are technically not allowed, but it would be interesting to hear enforcement clarification.
Anyway incredible footage, very well flown. Well deserved revenue if he gets it. I've heard he is out there all the time working hard (all grapevine hearsay to me).