Hi you are correct.
 
When you post any document in BC, it creates a journal and posts it.
Therefore, anything you can do as a document, you can generally do as a journal.
For example, sales order and Sales Journal achieve the same outcome, except you cant print the invoice for a journal
 
With reminders the same applies.
Post a normal reminder, check the Entries on the Issued Reminder
Then post a reminder general journal, and you achieve the same result
Then you can test if your journal is working the same as your document.
 
Last question, why would you do a reminder as a journal, it only will create a ledger entry, it doesnt actually provide any tangible outcome for the client or their customers to use this as a journal only.