If I were a conspiratorial type, I would say that (especially given the new changes to Points Advance) Marriott is waiting until March 6 to award the remaining bonus points so that they can't be used toward the current favorable award chart.

More likely it's just incompetence, but if it was going to be this hard to award the points for the bonus they created, why didn't they just make the bonus points earned based on some other metric?