I was watching this today.
After it sucks in some amount of source drive data, it then changes the detail window to say "writing to destination drive". Then it switches back to showing the next source drive file/folder.
Since the source drive is a SATA (drive #0) and my backup was an internal PATA, they are on different channels/controllers.
It's certainly possible the display of the files/folders is "lagging" behind what is actually occurring within Windows Backup but I doubt it.
FTR, I haven't done any I/O trace of anything (or even used Task Manager to see what the I/O activity looked like).
Any thoughts on how this was designed???