Hi,
tipotodo
My understanding is that it is faster because of less # of applicants with respect to available visa numbers (in EB1). EB2 and EB3 usually it is the other way round. Hence people will wait for priority date to be current before they can advance to 485 stage, hence the whole process appears to be long compared to EB1. Again this is with FBI background check not in the equation, if you add it to the equation, even though you have all your application in good shape, USCIS might pre-adjudicate your case, but it will wait till they receive info from FBI. FBI will not consider if it is EB1 or 2 or 3, they look at the application and it will follow the line, so in my understanding FBI is the universal equalizer of all the applications. In my latest reading there are 440K name to be screened, for background check.
Just an observation, not to scare you with this info, as an exception, there are cases where people got it in two or three weeks. I have no idea how that works?
wish you all the best in the second stage of GC
Rama