OS X doesn't really have the concept of windows being maximized; that is, being
in a mode where they can't be moved or resized.  As a consequence, it doesn't
have a button in the window title bar to restore a maximized window to normal.
So, when a Wine window is maximized, the Mac driver hijacks the green zoom
button to act as a restore button.  (When a window is zoomed, the green button
"unzooms" back to its last user size and position, so it's analogous.)

However, with OS X 10.10 (Yosemite), the green button prefers to act as a
toggle for the Cocoa full-screen mode rather than zooming and unzooming.  This
made it difficult for users to restore a maximized window.  They would have to
Option-click the green button, double-click the title bar, or choose Zoom
from the Window menu, none of which is obvious.

The fix is to disable Cocoa full-screen mode for maximized windows.  Then, the
green button reverts to unzoom and restoring the window.