I agree. Don't accept the ITA. IRCC decision will not care about your assessment only ECA report is a factual interpretation of your education.Wait for WES' response, recalculate your score using the calculator if it's different than expected. If you are still above 457, you are good to go. You have 60 days to apply, don't sweat it.
Fight WES tooth and nail but don't risk misrepresentation you have everything to lose and not only with EE.