I actually think that was a hell of a spot by the LJ and replay did not get that right. I was shocked watching it live when they overturned it.
I think the spirit of the rule is that when the runner/ball is crossing the plane of the sideline, we are to spot it where it crosses the plane of the sideline.
Scenarios where the ball did not cross the sideline but a part of the runner's body touches the sideline... that's where we spot the ball exactly where it is when the runner went OOB.
The rule is poorly written.
I'm with you, Bossman, and that is based on the rule, which I actually think is well written. "Exception: When the ball carrier is airborne as 'they'
(he) crosses the sideline (including a striding runner
(should be "ball carrier")), forward progress is determined by the position of the ball as it crosses the sideline."
In the video example, the BC is both voluntarily diving AND was driven into the air by the defender, so he is an AIRBORNE player, no matter how you look at it. During this process, the BC had the ball tucked against his body as he leaned and was falling forward and out of bounds. With reasonable certainty, the ball crossed the sideline before it reached the LTG (which appears to be 'exactly' the B-7, which is another discussion). The BC continues to fall forward over the OB area, eventually landing on the ground OB with the ball, itself, at that moment, beyond the LTG, with no part of his body other than hand or foot touching the ground inbounds. As an airborne BC, by rule, he gets progress to the point where the ball crossed the sideline while he was 'flying' out of bounds. Although I think the ball may have been inches closer to the LTG than the L marked it, I believe we can all agree that is was short of the LTG, and a really good spot.
IMHO, I believe the RO made an error. Forget the 2019 editorial change regarding a striding BC. He wasn't striding. He was quite literally off his feet flying OB.
Regarding the rule language, I believe it is just fine. But, all of the AR's seem to involve the goal line. They need an AR for these situations that do not involve the goal line, just to offer full clarity.