From the linked security report in that post https://www.netspi.com/wp-content/uploads/2025/11/google-fea... it seems like they implemented something similar to https://github.com/seemoo-lab/opendrop (which was also used to test interoperablity

Also `we welcome the opportunity to work with Apple to enable “Contacts Only” mode in the future` doesn't make it sound like Apple actually helped implement this