Failover Cluster Owners
The names you're seeing under "Other Resources" are actually the SQL Server instance names, not the names of the nodes that could be possible owners.

"Possible Owners" are the machines that are eligible to run the Roles configured in the cluster.  For SQL Server, Roles are the SQL Server instance, the SQL Server Agent service, etc.

"Other Resources" are items required to run each role.

The official Microsoft Docs on Failover Clustering with SQL Server is a great resource for understanding how that all ties together.

This MSDN blog talks about preferred and possible owners, and shows how SQL Server manages them automatically.

This Microsoft Docs page talks about the relationship between AlwaysOn and Failover Clustering.  This section of the above page says:


  Do not use the Failover Cluster Manager to manipulate availability groups, for example:



Do not add or remove resources in the clustered service (resource group) for the availability group.
Do not change any availability group properties, such as the possible owners and preferred owners. These properties are set automatically by the availability group.
Do not use the Failover Cluster Manager to move availability groups to different nodes or to fail over availability groups. The Failover Cluster Manager is not aware of the synchronization status of the availability replicas, and doing so can lead to extended downtime. You must use Transact-SQL or SQL Server Management Studio.