Supply chains are one thing, you also have to move tenants before you can start work there, which requires some interior fit-out work on the lower levels before you can move ahead, and we understandably don't cover interiors much on aB and how long that can take. You also can't start interiors until the floors are sealed back up, then roughed back in with new utilities and whatnot, which can be quite a process on a reno project with active tenants.
There's some visible progress as of recent though. Should be moving along from the outside soon enough.