I'm no insider whatsoever, but I was in the park as recently as yesterday, and you can still see Silver Shamrock signage on the facade if you peek through the gates as you leave the Stunt Show. You can't see much more than that, but it's definitely there. So unless the factory -- which (as far we we know, I guess) does not exist in the Michael Meyers continuity -- somehow plays a big role in Halloween Kills, I guess I just don't really get why the spec has turned this way? Because some of the signage came down, and also there are Halloween 3 easter eggs in the Halloween Kills trailer? Seems like a lil bit of a stretch.
Seems more likely to me that Universal realized folks were noticing the visible Halloween 3 signage and told construction to take them down until the house is announced. But again, no idea.