Seems interesting to me but its not sounding like much of an advantage, here's my train of thought:
Petrus user, builds 2x2x3 block. EO. Then builds last 2x2x1.
Now, normal petrus user builds last CE pair and is left with 7 OCLL cases.
EJF2L user builds last CE pair w/o regard to corner orientation and then is left with 16 CLS cases.
.. How is this a great advantage, over twice as many algs for a step (normal CE pair vs. EJ pair) that doesn't seem to be that much easier or quicker to recognize.
I know theres also the case of having an EJ pair in the 2x2x3 block, but still?
Have you ever tried blockbuilding? It can make things incredibly convenient, this does not in any way just apply to the last slot, or just the 2x2x3. It can be done anywhere. Meaning you can make a twisted 2x2x2, or in either "slot" during step 4. My favorite case happens to be the "EJ Square"=]. Say you get to step 4 and you have a 1x2x2 with a twisted corner. You can save like 2 seconds just by throwing it in there, and this does happen quite a lot. Another thing; a couple seconds means everything once you hit sub 20, and its the difference between a good and a bad average for people like Erik. And as far as recognition, its just like learning how to blockbuild, you get an eye for it. Lastly, I don't think you realize that EJF2L is not used in every solve. It is used when it is appropriate, meaning the solution is faster, easier, or just overall nicer. It's a blockbuilding technique, merely an addition to Petrus, and the time it takes to memo 16 2 gen algs, is certainly worth the time for this convenience in my solves. Besides, I doubt you use Petrus as your main method ;]
Maybe that clears things up a bit?