Keeping in mind the Connection is created in/retrieved from a ConnectionFactory...
According to the specification you can get multiple connections from same resource connection factory object as you are doing in your abstract sample code. The point that you are making is I guess that since you are getting a new connection from the connection factory in the method call itself would the connection retrieved from this connection factory be affected by the rollback/commit. Spec 421-422
Invoke the appropriate method on the resource manager connection factory to obtain a connection to the resource. The factory method is specific to the resource type. It is possible to obtain multiple connections by calling the factory object multiple times.
I don't see that how would whether you create a new connection or use an cexisting one would affect the transaction management. Except I would like to know if <res-sharing-scope> will have some role to play if it is defined as Unshareable.
Am I making sense here?