If this health check highlights that an ESXi host has connectivity issues, vCenter Server does not know its state. The host may be up and may be actively participating in the vSAN cluster, serving data, and being healthy and performing its storage functions as part of the vSAN cluster.
However, it could also mean that either the vSAN management daemon on the ESXi host may be down and unavailable. The vCenter Server, and hence the vSAN Health check, cannot fully assess the situation as long the host is disconnected.