Are implicit DB commits initiated when there are Sync or Async RFC call

BC414,Page 3-8 says, whenever there are synchronous and asynchronous rfc calls,implicit DB commits are always initiated.

But I test it in ABAP program as following steps.

1: insert data into dbtable.

2: Call Function "RFCFunction".(within this function, insert data into dbtable).

3: Rollback Work.

All the data is not inserted into db table at all.

Are there anything wrong with my understanding?