Running xfce4-terminal from git tree. As of commit: https://git.xfce.org/apps/xfce4-terminal/commit/?id=71bc9086016062faa90485d27d4fe522609d44d7 (Fix size increase when the menu is used on Wayland) xfce4-terminal always starts with the menubar shown - even if it's disabled in the properties. Flipping the properties setting to on, save, then off again makes the menubar hide for that instance of the app. I have confirmed this with a git bisect.
Igor referenced this bugreport in commit c54e6edf0b6247bdeddb23f419d4d5a2040d05b8 Fix 'Menubar starts shown when set to hidden in properties' https://git.xfce.org/apps/xfce4-terminal/commit?id=c54e6edf0b6247bdeddb23f419d4d5a2040d05b8
Hi ToZ, thanks for the report! I missed this use case, indeed.