I believe that you get to see most of the line with EP on Forbidden Journey. I think you only miss the greenhouse. I wouldn't say I've been missing it Bob As was already said, you see everything of interest in the Gringott's EP queue. The scare-actors do not always appear at park/ride opening for Kong. I recently asked this question on a Universal Podcast, not sure if I can mention the name here or not. They also suggested Men in Black and Mummy for their interactive stuff. ET is supposed to be cool and usually doesn't have a long enough line to bother using Express Pass. Spiderman is supposed to be cool too. They emphatically suggested to avoid the Rip Ride Rocket full line and use EP always.
But many people enjoy the queues for some of these rides as well, consider them part of the experience, or not to be missed. I can see why the question is asked, even if a person with Express wanted to see the full queue just once. Could you imagine if the Forbidden Journey EP line skipped the entire castle? It does not, but if it did I would not enjoy the ride near as much.
If you’ve never been in them you don’t know if you would want to experience them. I’m happy having skipped them.
What another person considers a Must Do might not be what I consider the same, but MY Must Do is to not waste time at the parks looking at lines you don’t have to be in.