When investigating JDK-8318854, it was observed that AWT NSApp's setDelegate is called when Swing content is embedded in FX window. The expected behavior is that FX creates the NSApp and hence no AWT's applicationDelegate should be installed. But this is not the case as can be seen from the debug log.

2023-11-01 12:25:40.243 java[92753:12085159] FX NSApplication initWithEnv()
2023-11-01 12:25:40.262 java[92753:12085156] >>>> isEmbedded App ??? 0
2023-11-01 12:25:40.279 java[92753:12085156] >>>> FX setDelegate called - IF BLOCK
2023-11-01 12:25:40.564 java[92753:12085156] AWT ApplicationDelegate init()
2023-11-01 12:25:40.565 java[92753:12085156] >> AWT OSXAPP_SetApplicationDelegate::setDelegate called >>>>