vSAN is a an object-based datastore, you don't have LUNs where to move VMs. Depending on the FTT that you choose you will have copies of the data on different servers.
You can take a look on this documentation Architecture | vSAN Frequently Asked Questions (FAQ) | VMware
Interesting problem to have, i had to do some googling on this as its not something i had attempted to do before but i think ive found a kb which describes what you need to do
It does state:
Currently there is no mechanism to prevent this behavior from happening as vSAN does not move VMDK Descriptor files between Namespace Directories. However, the need to move files between Namespaces should be a relatively rare scenario.