The WooCommerce plugin uses a role of "Shop Manager" which I am locking down to only allow access to necessary menu items. I do not want this role to Add Posts, but they should be able to Add Coupons. When the "Add Posts" menu item is removed, the user is unable to add coupons as well. Some investigation shows that
$this->get_current_menu_item(); is not returning the correct menu item (there is no menu item for "Add Coupon") and instead returns the "Add Post" item for which the role does not have permissions to modify.