In section E.18.104.22.168 Transaction Requirements, there is the following statement. Liberty fully supports this "local" transaction propagation.
Note that this transaction propagation requirement applies only to invocations
of enterprise beans in the same Java EE product instance as the invoking
component. Invocations of enterprise beans in another Java EE product
instance (for example, using the EJB interoperability protocol) need not prop-
agate the transaction context. See the EJB specification for details.