Service Offerings in Service Point do not disable fields after being submitted. In Service Catalog, we can see that those fields are disabled for the same user/role.
Service Catalog 17.4
Service Point 17.4
This is by design. Service Point does not have an intermediate window like a catalog where you click on a button to make the form editable if there are permissions. In Service Point, if the user has permissions, the form will be editable.
Only Superadmins like Service Delivery Managers and Request Managers will have the form in edit mode during pending approval and fulfillment range, even though they don't have pending action assigned to them. This is just equivalent to overriding/push-through the case in Service Catalog. For other user roles, the form fields will be disabled as in the Service Catalog.