After working in Xcode when I want to quit Xcode by Command Q or the menu item Xcode will display a flashing Open Quickly window, the Quit Xcode menu item is grayed out and the only way to shut down Xcode is to force quit it. I am running macOS 26 beta 3 and Xcode 26 Beta 3 on a 24 inch iMac with M3 chip s/n K626GKFP3J
This isn't just an Xcode issue This sometimes happens in other apps, too, when some other background process hasn't finished exiting and the main app (Xcode) just waits for it to finish.
As you found, the way to close Xcode is to Force Quit it. That won't do any harm. It likely won't do any harm either if you just leave it - unless you want to shut down your Mac.
You probably don't need to raise a bug for this, but you can if you like, at: https://feedbackassistant.apple.com/ and post the FB number here.
FYI, you don't need to mention your Mac's serial number, especially for software bugs.