This is actually a change in the core functionality of Windows in this development cycle.
Old behavior:
- When you shut down your PC, all apps are closed
- After reboot/restart, you have to re-open any app you'd like to use
New behavior:
- When shutting down your PC, any open apps are "bookmarked" (for lack of a better word)
- After reboot/restart, these apps will re-open automatically
If you want to start with no apps open (other than those set to auto-start via Task Manager/Start), you'll need to ensure all apps are closed before shutting down or restarting the PC.
Why?
The desire is to create a seamless experience wherein, if you have to reboot a PC, you can pick back up quickly from where you left off and resume being productive.* This has far-ranging impacts across the OS (in a good way).