This is NOT true. Actually, this is one area that I like the way Marriott has implemented the benefit.

The hotel has NO direct control over this benefit. When you check for a room online, if you are a Plat, the only time a hotel won't show availability is if they go to Marriott Corp and ask for a waiver. And to get that waiver, they have to show that their hotel is pretty much booked up by a particular group or event. Only then will Marriott grant it and then Marriott corp will turn off the Plat override.

As I mentioned earlier, you only get one room per night with this benefit. So if you already have a room at that hotel (using a Plat override) you won't get a 2nd one. And as some others have mentioned, Marriott's system will tell you when you are using the Plat override, but it's very easy to miss that notice when you are making the reservations. So quite often you may get one and not even realize you used that benefit.