Not surprisingly, the announcement was being shared with heavy criticism of this shul putting people in danger and for using a reckless policy.

Personally, I don't think it was a bad thing, not that it should have been done. But the fact that it was, gives people an opportunity to take precautions. A lot of Covid positive people were surely going to be going to services without telling anyone they are Covid positive - this has been happening in every other venue and there is no reason to think it would not happen with Yom Kippur services. That is besides for the people who violate and flout the rules openly and publicly just because they can or because they don't believe in the seriousness of the entire matter.

Having a shul announce that it is welcoming Covid positive people to pray with them would give others who do not want to be in the presence of someone Covid positive to find a different place to pray. It was almost definitely going to happen anyway, and this way it happened in a way that would allow other people who so desired to take any necessary precautions. And maybe all the Covid positive people who would feel uncomfortable and unwelcome elsewhere would see this type of a shul as a solution and all concentrate there to daven in a welcoming atmosphere.

I would like to know after the fact what happened - was the minyan full of Covid positive (and recovered) people? Did covid negative people attend as well? If they did, did the virus spread? How many people from that minyan got sick and/or seriously ill? I doubt we will get any such information.