Originally Posted by
BigLar
2. In the T&C's, they say this: "To qualify to earn bonus miles under this promotion, you must be a Marriott Rewards member and choose to earn American Airlines AAdvantage miles in your Marriott Rewards member profile.", which seems to indicate that the promotion only applies to those who select miles instead of points for their earning preference.
The directions on the webpage you provided in the OP, detail steps to order a points-to-miles conversion award, not a way to change to receiving FF miles instead of points for a particular stay.