that it was expressly forbidden to manoeuvere based upon a TA only.
There seems to be some misinterpretation of the FCTM. Manoeuvring solely on a TA means using the traffic display as your sole guide. The 737 QRH recall procedure is quite clear. If in receipt of a TA establish visual contact and manoeuvre
if needed.
For an RA the procedure is to maintain the planned track (
turns and all)
unless visual contact means you have to alter your planned track to avoid.
This means that one does not manoeuvre in response to a TA only. Neither does one do anything but what the RA says. Unless in both cases you can see the traffic and it is clear that there is a greater risk if the current flightpath is maintained.