Here's a clear summary based on your source and Windows community/engineer explanations:
Why You See a Blank or Unnamed Program Blocking Windows Shutdown
When you shut down your PC, Windows sends a message to all running programs and background services asking them to close safely.
Sometimes...
background processes
dummy windows
process management
raymond chen
shutdown resolver
shutdownblockreasoncreate
software development
system security
system stability
task manager
unsaved work warning
windows apps
windows background services
windows central
windows comments
windowsexplanationwindows shutdown
windows system issues
windows system tips
windows troubleshooting