Hmmm. But if you get 'climb, climb now' with one donk and a full load you ain't gonna be doing it are you? Put it in TA only and you can still see where the traffic is so you can turn (bit dodge in London TMA) if you wish but there is the added benefit of the stronger RA in the other A/C (assuming TCAS fit) which still has full manoeverability.
Makes sense to me anyway...