NOTE: For future reference: should probably be posting this type of question over in the SAP Replication Server forum; so don't be surprised if one of the admins moves this thread over there
Since a WS setup needs to support the 'switch active' command at some point (whether you plan to use 'switch active' or not), the replicate database must also be configured to support outgoing transactions (ie, also be configured with some of the components of a primary database => repagent configured, repagent/inbound thread defined in repserver, etc).
I'd suggest you try running rs_init again (for adding the standby db) and this time answer 'yes' to the question "Will the database be replicated". By answering 'yes' to this question the connection should be created with the 'log transfer on' clause.
The downside to this step is that once you get the standby db added to the repserver you'll want to go in and make sure a) the repagent is not running in the RDB and b) there is no active secondary trunc pt in the RDB. [Obviously (?) you'll also want to do this - stop repagent, drop trunc pt - after any loading of a PDB db dump into the RDB. "Duh, Mark!" ?]
If/when you do run the 'switch active' command in the future, it should take care of re-enabling the trunc pt in the RDB (soon to be the new PDB) and starting the repagent.
Yeah, rs_init should be a bit 'smarter' when adding databases to a logical connection (eg, know to automatically create the connection 'with log transfer on', config but don't start the RDB repagent, do not leave a trunc pt enabled in the RDB, etc) ...