Interesting. So for a first down, you can get the benefit of two more inches for a sideways ball spot, but on a touchdown you don't and the foremost part of the ball must pierce the plane, regardless of ball orientation. The rest of the time a play is measured from foremost point to foremost point, planting the ball with its tip forward on the current line.
Don
You appear to be hung up on thinking the tip of the ball is the point that is used to
determine forward progress. Not at all true. It could be - if it happens to be the part of the ball that is nearest to opponent's goal line when the ball is declared dead. Instead of thinking of the ball, think of a vertical (geometrical) plane that is pushed forward by the offense, or backward by the defense, but the entire ball is on the offensive side of that plane at all times (and the plane is always touching the ball), regardless of its orientation. Progress is determined by that plane, not by the orientation of the ball. So, when the ball becomes dead, since, by rule, it must have its long axis parallel to the sidelines when the snap begins, it is rotated to get the long axis of the ball perpendicular to the progress plane. Nothing has changed about the progress plane - it is still where it was when the ball became dead. Since the ball remains the same during the game (at least we hope it does), neither team gets an advantage or benefit that the other team doesn't get.
And don't forget that the ball has mass, which is why we have two lines of scrimmage on every scrimmage down - the front end of the ball for Team B, and the back end of the ball for Team A. The game is both teams attempting to move the three-dimensional ball back and forth between the goal lines When the ball becomes dead 6" from B's goal line after 4th down, it is spotted with the B point of the ball 6" from the goal line - long axis parallel to the sidelines - and then the chains and down marker are set on the A end of the ball, 1st and 10 for B. Same after an incomplete pass on 4th down. The ball is spotted back exactly as it was to begin 4th down, then the chains and down marker are moved to the opposite (A) end of the ball, 1st and 10 for B. (Don't simply flip the ball over with the down marker in the same location).
The ONLY exception to any of this is when the ball carrier is tackled at his own goal line, with the ball in the field of play, but sideways and just a couple of inches away from the goal line. If you were to rotate the ball from the true progress plane, the back end of the ball would likely be over the goal line. We aren't going to award a safety when no part of the ball was breaking the plane of the defending team's goal line when it became dead. We just move the ball out a bit, with the back tip that same few inches from the goal line.
Simple.
