I have two ORA apitasia eating filefish (Hans and Franz) for about 7-9 months, and have never seen them nip any of my LPS corals or GSP. I did a ton of research before getting them as I was concerned they might go after some of my corals, just like everyone else. I came to the conclusion many of the wild caught filefish sold in the LFS might not be Acreichthys Tomentosus and where ID'ed wrong. I call ORA and talk to them about the odds of them nipping corals and they said it was a possibility, which I assumed was a CYA. I took the chance anyway, and have been very happy with them. They are very interesting fish and add character to the tank. I've also recently seen some interesting behavior from them, and I'm now wondering if it's mating behavior. When I have time, I might post a video and see if anyone knows.
They spend most of the day cruising around the tank hunting pods, which brings me to a second point about the possibility of some of the coral nipping behavior being false. I've seen them on many occasions go after pods on or near corals, and it looks like they are going after the corals, but they are not. Could it be others have seen this behavior and assumed wrong?
That said - The final point I will add regarding my experience is I feed generously twice a day. I'm sure if I was one of those reefers that barely fed my livestock, I might see different behavior. Think about it, when you get really hungry you're more likely to try something you wouldn't normally eat... Right? I'd be more worried about the Toby Puffer I think.
I hope this helps with your decision... Good luck!