Interesting observations. If we were talking Workbench Installs would we be including our programs, work and data, virtual memory on hard disk, recovery (backup) partitions or resume files in our OS Footprint? I'm guessing not.
These days the Windows Partition for Win10 on a normal install is 4.2 GB (on disk). With a default Windows Program Files size of less that 2GB. Thats on a Bitlocker encrypted c:/ drive.