This is not documented.
But the cause is the same of the Message #1053884

Expected:
MENU BAR and HalfHeightCaption are mutually exclusive ( uses the same area )
then :
an Error "Form attribute incompatible" and ignore the command

Observed: Visual FoxPro try to put the menu, but it have a paint collision in NC area
( go over the form icon and you see the pad's prompt "Open")

Repro:

PUBLIC FTOP
FTOP = NEWOBJECT("ASTOP")
FTOP.SHOW

DEFINE CLASS ASTOP AS Form
	
	showwindow = 1
	Desktop	   = .t.
	Caption = "PAINT COLLISION NC"

	PROCEDURE LOAD
		DEFINE MENU ASTOP1  BAR IN (thisform.name)
		DEFINE PAD open OF ASTOP1 PROMPT "open"

		thisform.HalfHeightCaption = .T.
		ACTIVATE MENU ASTOP1
*		thisform.HalfHeightCaption = .T.
		
	PROCEDURE UNLOAD
		RELEASE MENU ASTOP1
		
ENDDEFINE