LOL, show me where you have seen this before. I'll wait.
Dude, the definition of a touchback is in the section right after where you pulled this rule which is an exception to the Safety rules. I knew I should have done this myself, lol. The Safety rule is concerned with a defender coming down with a ball in his own end zone and not having a Safety called against him. Lewis was nowhere near that scenario. The touchback definition reads as follows (note my underlining):
RULE 11
SECTION 6 TOUCHBACK
Note: A touchback, while not a score, is included in this rule because, like scoring plays, it is a case of a ball that is dead on
or behind a goal line.
ARTICLE 1. DEFINITION. It is a Touchback if the ball is dead on or behind the goal line a team is defending, provided that the
impetus comes from an opponent, and that it is not a touchdown or an incomplete forward pass.
Note: A ball in the end zone which is carried toward the field of play is still in the end zone until the entire ball is in the field of
play (3-12-4).
So you see that a touchback is when the ball is dead
on or behind the goal line. This says nothing about if a player's foot is on the line or not. It speaks of the ball only and where it goes dead. There are rules for when the "ball is dead" as well (
Rule 7, Section 2 - Dead Ball) and among them is "when a runner is out of bounds." These 2 rules work together of course. So you'd just have to answer where Lewis went out of bounds to get your spot of the ball. If on or behind the goal line, see the Touchback rule. If not on or behind the goal line, see the Dead Ball rule. Again, note here how Lewis is to the outside of the pylon. Therefore, so is the ball even if it was in the end zone at any point. Your "sources" are not going to give you greater in-depth detail than this I can assure you.