Thanks for that background on Union Square
@Contra. What do you think we're looking then? That's a reinforced concrete wall that goes up 2 floors, leaving about 15 feet of clearance. That's a load bearing plinth if I ever saw one. If it's not built to the ceiling, then what load is it going to be supporting?
Looking back at
@Benito's images from above, this wall wasn't built with the structure. It was added later, so we know it's not supporting the structure. So what purpose does it serve if it's not structural, and stops 15 feet short of the ceiling?
It's important to note that Apple hasn't taken possession of the space yet. Mizrahi is no doubt building the space to their specifications but customizations will only take place once they move their team in.
The steel you saw at Union Square would be a part of building the actual store. We'd get steel beams sitting on that plinth, going back into the adjacent building, tying to its elevator core, and forming a cantilever into the Apple space.
Here's a rough drawing of what I'm describing: