workaround:

1) create a fresh subaccount-A from snapshot-A

2) now this subaccount-A will be forever tied to that snapshot-A

3) make a new snapshot-B from subaccount-A

4) make a new subaccount-B from snapshot-B

5) delete subaccount-A

6) now snapshot-A won't have a link to subaccount-B

This, however, is only for brand new account creation, as snapshots don't allow full subaccount cloning where contacts, conversations, business settings, etc would be copied from subaccount-A to subaccount-B.