great, BUT that was only part of the unanswered question inasmuch as RCs are not by Cat but by Tiers so if walked from a non-Marriott if limited to Cat one cannot use it at an RC.
BTW, it's been stated by Marriott Concerige that Marriott Insider is NOT an authorized Marriott spokesperson so rely on their publications accordingly.
I got an official answer from Marriott at the Rewards Insiders forum. They say it's a recent change and that the certificates are for any category hotel.