The storage resources pooled by vSAN are only available to VMs within the cluster. The exception to this is with the iSCSI service which can be optionally exposed, other workloads outside of the cluster (however, not other ESXi hosts) can consume that storage.
Welcome to Communities and vSAN.
VMs only have access to the vmdks assigned to them - this isn't so dissimilar to how it is with SAN-backed LUNs (where VMs can access any data on vmdks assigned to them provided the datastores are available) other than it is one big datastore as opposed to multiple.
Thank you for the answers!