Just encountered a situation in my vSAN (esxi version 7.0.3, 19193900) cluster of 4 nodes.
When I perform "full data migration" precheck for a host to enter maintenance mode, the result is negative, as shown below:
The host cannot enter maintenance mode.
1 more standalone host is required. Some objects will become inaccessible or non-compliant with their storage policy.

I checked the VMs that are residing in this cluster and they all use the "vsan default storage policy".
This is strange.
does anyone know why? or any clues to trace objects that cause this?