Me also getting same problem whenever I try to update Xcode. At least it should show update size of any app. It doesn't show update size for any app in App Store. How can we know which update is consuming how much data? If it explicitly asks that I want exactly this much of space for installing updates then we can do something about it. Without showing update size it simply goes on asking for more space for whatever free space we provide. Anyway this problem was encountered when I updated from
Catalina 11.15 to Big Sur 11.0 (trouble moving Xcode from 12.4 (12D4e)) to 12.5
