I just spoke to Siteminder on the phone regarding the stop sales issue we have with Booking.com.
They informed us that we can ask Booking.com to set up in the system so that promotion stop sales status will follow the parent rate. That should solve our issue.
Please get in touch with Booking.com to have this updated. Please also check if it works the same way when we reopen sales.
Let me know if you have any questions about this.