Split View only goes to full screen

I have a new Mac book air M3 running Sonoma and up to date.

Apps with arrows in the green button only go to full screen no drop down menu appears.

Mission Control allow spaces has been enabled and computer restarted but still not working .

I have hunted everywhere for an answer to this but haven't found a solution.

Several questions on here asking the same thing but never any answers. Please could someone explain why this is a problem. Thanks