If you open Task Manager and go to the Startup tab, it lists the programs that are registered in the Startup group or the Run key to run automatically when you sign in. But you might see an entry ...

Boost Windows 11 boot speed by delaying startup apps. Manage background programs via Task Manager for faster system ...

If this setting includes an entry to hide the Startup page, this is the reason ... create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers ...