Yes that's right, just did a quick test here, and if you create a job for the fourth and last Wednesday of the month (eg tonight in both cases), you'll see there is only job generated.
When BEWS finishes a recurring job, it calculates the next time it is due to run. Even if the job has two elements which point to the same time and date it doesn't matter, since by the time that first job has completed, the next due date will be the following Wednesday in this case, not a time in the past.