It is a tough concept to grasp, especially with the rule and AR language provided. Let me see if I can get to the bottom line.
First, when a TD is scored, all 5 and 10-yard penalties by the non-scoring team are declined, by rule. So, when B's holding penalty is declined (by rule), there are no 'accepted' penalties to cancel B's illegal touching privilege (to take the ball at any spot of A's illegal touching). Obviously, B would always accept that privilege, to prevent A's score. But, in that case, many folks claim that Team B gets an unfair advantage over Team A by 1) getting to cancel A's score, 2) getting to keep the ball, and 3) receiving no punishment for the holding foul. So, to rectify that, an 'exception' of sorts was put in the rules, for these cases. No Team A does not get to score. No, Team A does not get the ball. But, Team B doesn't go unpunished for the holding foul. Using the end of the related run as the Basic Spot, Team B's holding foul is then penalized from the appropriate spot, and B takes over from there. If the spot of the illegal touching is more advantageous to Team A, then they can decline the penalty, and let B have the ball at the spot of the illegal touching. (Added after I first posted this message.)
So, Team B's penalty is at first declined (by rule), but then accepted (or declined) later. Make sense? No, but most think it is fair.
Me, personally - I think that's what Team A gets for illegally touching the ball. If they don't commit the illegal touching violation, then they get the score. Stay away from the ball until it is touched by B. Very simple.
Robert