I'm going to take a stab at why the curtain wall has not progressed in over a month.
I think they are letting the core rise higher first to add stability to the building. I have heard that there is/was a lot of movement of the tower because of the wind load. The higher the curtain wall goes the more force is put on the building. Allowing the core to rise first as well as leaving the upper floors open would help alleviate the issue.
Again, the is just a hypothesis but makes sense (to me anyway
).
Maybe Allan could elaborate?