Most likely because packages for 2024 don't go on sale until end of this month I believe so this gives time for people to know what the deal is going to be for next year before booking packages.So if this is truly a lack of attendance thing why would they wait until 2024?
It is also interesting that they are not starting this until after marathon weekend I guess because they figure people who have already registered for the races are already "locked in" on rooms even if they can't officially reserve them yet. (though my TA already kinda has and I am sure is not alone).