This article explains the purpose and details of protection group membership change health check and provides details on why it will report the info.
VMware vSAN 9.0 and Future Releases
Q: What does the 'Protection group membership change' Health Check do?
It checks the VM membership changes of protection groups, will be captured as info level health event. Users can proactively check the events via the health check or "History details" of this check.
Q: What does it mean when it is in an info state?
This is to inform that VMs are added or removed from the Protection Group. It will show up only once as info state in health findings and we also provide historical view to check historical membership update.