Yes that's normal. CBSubs only manages usergroups that it has plans configured to manage. So if nothing is managing Registered then a plan manages Author it won't remove Registered when Author is added. There should be no harm in them having both. For a more strict management of usergroups you'd need to use CB Auto Actions. I can provide an auto action example if you really don't want them to have Registered.

Please attach images in the future and don't copy paste them. That functionality doesn't work so great in Kunena and our security doesn't accept data URIs for security purposes.

Use the below usage to act on subscription state changes within CB Auto Actions.

Plan Active
Global
Triggers: onCPayUserStateChange
User: Automatic
Access: Everybody
Conditions
Condition 1
Field: Custom > Value
Custom Value: [var3]
Operator: Equal To
Value: PLAN_ID_HERE
Condition 2
Field: Custom > Value
Custom Value: [var2]
Operator: Equal To
Value: A

Plan Expired
Global
Triggers: onCPayUserStateChange
User: Automatic
Access: Everybody
Conditions
Condition 1
Field: Custom > Value
Custom Value: [var3]
Operator: Equal To
Value: PLAN_ID_HERE
Condition 2
Field: Custom > Value
Custom Value: [var2]
Operator: Not Equal To
Value: A

Be sure to replace PLAN_ID_HERE with the actual id of your plan as found in CBSubs > Plans. In your case you'd just use the Usergroup action type then adjust its parameters further as needed.