Step to reproduced
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1) Enable Screen magnifier on theMac
System Preference -> Accessibility -> Zoom -> Select ( Enable Hover Text)
2) Run the attached test
3) Once the Frame is visible click on the 'File' menu' so see the menu and menuitems.
4) Press 'cmd' button and move the mouse pointer over the 'New' menu which will shows the sub menuitem. Observe that 'New' which is the Menu name is not showed as magnified text and even arrow button is also not seen. If you see the same then the bug is reproduced.

I compared with TextEdit System and other applications.
I have attached the screen recording.

This will be very much useful for the accessibility user to know that there is a submenu.

Note : Very rarely JMenu is seen but arrow is missing. I have attached the screen recording .