Myallocator currently does not support sending Rate or Availability changes (such as closing rooms) to a specific channel. When sending Rates/Availability, myallocator sends all changes to all connected channels.
If you use BookNow, there is an option to close out availability to all external channels and only leave rooms open on BookNow.
Please check the following article to learn how to set that option: Is it possible to close rooms to outside channels and only sell them on BookNow?