So despite the continuing ongoing garbled language in the rule 10 enforcement procedures, the actual result is that the momentum exception in this case is canceled and the enforcement spot is the EZ resulting in a safety?
Wandering a bit off topic here, and I'm sure people might disagree philosophically, but I would argue that when the momentum exception kicks in the "end of the run" remains the spot of momentum regardless of the position of the ball. The exception, I would also argue, doesn't actually kick in until the ball becomes dead in the end zone in B's possession. If the "end of the play" aspect of the exception doesn't happen, then the momentum exception never applied in the first place (or the ability for it to be applied was cancelled). This is more philosophical than strict rules reading, because there's not much in the rules about momentum, especially in complex scenarios.
In case of a penalty, we'd enforce the foul considering the end of the run being the spot of momentum, not B's end zone. If the penalty was a dead ball late hit by B at the B20, we'd enforce half the distance from the spot of momentum, not a safety. Or, if B56 blocks A88 in the back after the interception, but at the B5, it would be half the distance from the momentum spot, not a safety. The issue in the above scenarios is that a team fouled in their own end zone while in possession of the ball, which is always a safety.
If you're just trying to point out that Rule 10 is a garbled mess at the moment... well,
