I've never been to the SF Union Square store. (I haven't been to SF in more than a decade.)
But I recall all the controversy over the design of the Apple store, and the fact that it might destroy a piece of public art. Apple redesigned the store to address the controversy.
That wasn't all that long ago. Why are they moving the store now?
As was pointed out earlier, the current store is on Stockton at Ellis, almost adjacent to Market and 4th. The new store is being built across the street from Union Square, on Post at Stockton, three blocks to the north.
FWIW, the fountain in question was originally going to be moved (not destroyed):

Since then the plans were changed to preserve most of the plaza -- including the fountain:

Daniel Eran Dilger at AI did did a great writeup on the subject including pictures, aerial shots, maps, etc.:
Apple's new Union Square store will not even reach fountain of controversy - AppleInsider.com