I was under the impression it was done out of necessity for Fallon (simply not enough space for two theatres and a full queue).
It's all well and good for a one-off attraction, but you cannot eliminate lines as FP demonstrates. Something has to give. The holding room concept is kind of neat, but it's essentially already something they've employed with a series of pre-show rooms. There's also a slippery slope to the holding rooms, you really can't hold people in them much longer (outside of live entertainment) than a pre-show room without them getting equally as bored.
The funny thing is that the virtual queue still seems to lead to a fairly prolonged wait for Fallon (yes I consider 30 minutes in excess of what I'd normally personally bother with standby). That's potentially annoying as well, being barred from rides you still are going to end up waiting for anyways.
I feel like they aren't thinking this through at all. Like I said, it worked well once, it's not going to work when 20, 30, 40% of park capacity shifts to the model.