I'll make one more reply and then let you have the last word if you want since otherwise this will go on all day.
Also let me note that I'm not arguing that the rule is good, only that it was applied correctly.
Right, I would say that running falls under the definition of "striding", so the exception is applied and the ball is spotted where it crossed the line once the play is dead. Note that the ball crossing the sideline doesn't cause the play to be dead -- he still has to touch out of bounds and then the play is dead and the ball is spotted back where it crossed the line.
Out of bounds is the ground on or past the sideline. A player's body or the ball being over the ground outside the sideline definitely doesn't count as the play being dead or out of bounds. That's why plays where the receiver is diving for the ball and manages to get his feet down before his body touches out count. You are not out of bounds and the play is not dead until a part of your body or the ball physically touches out.
As for definitions of airborne and striding, I would say that if a player is not touching the ground then he is airborne. And I would say striding is running, one foot after the other. If you have your hand down in bounds, I would say you are definitely not "airborne", and I would also say that diving forward with both legs off the ground and a hand on the ground is not "striding" by any definition I've ever seen.
Your argument seems to boil down to two things:
1: Although the rulebook has separate rules for how this is handled in the endzone and between the goal lines, it's apples to apples and the endzone rule should apply in both places.
2: Although the rulebook states that in between the goal lines the ball is only marked out of bounds where it crossed the sideline as the exception to the rule, it means that should always be the case and the normal rule should never apply.
Neither of those arguments hold water to me.
I think we're just making this too complicated.
In both situations the ball is placed at it's most forward point of progress where the BALL crosses the sideline when the player is declared out of bounds. This is the key. The exception simply states at what point the ball's forward progress ends because of the player's state.
When some form of airborne or striding, the ball is essentially dead or no more progress can be gained at the last point the ball crossed the sideline and the reason is clear, to prevent free or un-defendable yardage from being gained. This is the same reason players hold the ball inbounds to the pylon when diving to score. It's not different and in fact is addressed in the same subpara of the rules.
Otherwise it's the most forward point of progress when the player himself goes out of bounds regardless of state. Another example I came up with would be a reception where the ball goes over the sideline and then the player pulls the ball back inbounds and continues running.
You have to roll the frames back a few from your picture because the ball actually crosses the sideline well before he reaches the line to gain. Nevertheless, In this exact case, the player had the ball tucked, the ball itself is across the sideline and his body is doing everything it can to try and keep the ball inbounds because he is well aware it is out of bounds and prior to the line of gain. I completely agree with the announcers, it was an amazing feat of physics that he stayed off the ground for so long and I can't explain how he did it but it doesn't matter because the ball itself was already out of play and he was unable to get it back inbound before his body was out of bounds.
Now, If he had extended the ball across the plane for the line to gain PRIOR to the ball and his body going out, perhaps with his left hand reaching, it would have been a legit gain and we're not having this discussion.
I find the rules writing interesting because they don't use the word stride anywhere else in the book except for this rule so I don't know if it was intended to mean something else but peculiar at least. You are arguing that i'm applying the exception to the rule too much, when in practice I don't know what actually occurs more. I would think runs to the sideline would be just as likely as passes and catches or kicks or fumbles, so maybe they should have put the airborne and striding first in line instead of as an exception. Either way, it doesn't automatically invalidate the interpretation.
By the way it's New Year, you shouldn't have anything else to do than sit on here with a double pour and talk football, otherwise you're doing it wrong.