I'm having a weird issue with Minecraft going into the "F11 full screen" mode automatically on startup, and I can't get that to stop happening.

There are two full-screen modes.

One uses the maximize button on the window, which gives Minecraft its own desktop, and I can use a swiping gesture or Command-Tab to switch apps. This is the full-screen mode I want to use.

The other seems to be some kind of legacy thing that takes over the machine. To get into this mode on a Mac requires the key combination "Fn+Alt+F11." I cannot switch to other apps in this mode without first exiting this mode. I don't want to use this mode at all. But Minecraft INSISTS on going into this mode automatically when it starts up.

This didn't used to happen. But one time I tried using the F11 mode, just to try it. Now it's stuck this way, and I can't get the old behavior back. It doesn't matter what I do now. I can switch out of this mode and use the "proper" desktop fullscreen mode, but quitting the game in this state, when I restart, it goes back to the F11 mode. I can also quit when MC is just in a window, and the same problem happens.

The fact that there is no way to return to the original behavior is definitely a bug. The fact that MC has a fullscreen mode that doesn't interact with the OS properly is ALSO a bug. Why do you have two full-screen modes, one of which doesn't interact with the OS properly?