I didn't notice that part before, good catch. Usually the benefit of grouping multiple VMs into the same job is for management reasons, as you can imagine having hundreds of VMs, and one job for each, could potentially become a cumbersone activity. But as you stated already, automation can surely help here and remove the complexity. Also, being it a migration, it would not be a permanent setup, you can switch back to jobs managing multiple VMs once the migration is completed.
EMEA Cloud Architect @ Veeam Software
Veeam VMCE #1