When recomposing a floating pool of linked clones, ALL the VMs are destroyed, a new clone (replica) of the parent VM is created and then the VMs are created from that new replica.
When the pool is dedicated, the desktop VMs that have already been assigned a user are not destroyed; instead, the new replica is created and the VMs are reconfigured to use the new Hard disk pointing to the replica; the VMs that have not been assigned a user are treated as floating LC, that is, they are destroyed and recreated from the new replica.