M4 Mac user here happy to shed some light onto this. It’s actually super intuitive: “Full screen” on Mac means the current App window becomes a new temporary virtual desktop, which is placed after your normal virtual desktops. It also turns off the status bar / app menu, although you don’t get that screen space back because of the camera notch, it’s just blacked out.

Note that how many virtual desktops you have and which one is selected is specific to each display. So if you like multitasking, it really helps if you’re good at remembering all of them in the correct order including any fullscreen apps and the display they’re on. And I hope you don’t mind performing the same swiping gesture multiple times to get back to your fullscreen app. Also you can’t move it between displays.

You might just want to maximize your app window instead. Though you do need third-party software to do that.

I wish I was kidding about any of this.

I don’t even know whether I understand I just hear MacOS users griping about fullscreen, and a quick google gave quite recent results. Especially with fullscreen being incompatible with other windows on top (each fullscreen window necessary is on its own workspace) which would be highly annoying in Blender. You can configure blender to have file open dialogues, render results etc. in its main window, but certain stuff like preferences always open a second one.