The autopilot(s) have at that point wound in nose-up stabiliser (i.e. ready for the autopilot to either flare the aircraft as part of the landing, or else primed for a go-around),
I am not sure of my facts here but I doubt if the 400 ft wind back of the stabiliser trim on a dual autopilot ILS is to specifically aid the go-around as such. The application of high thrust at the initiation of the go-around produces a strong pitch up. You don't need additional back trim which has already occurred at 400 ft on a dual channel approach.
Interestingly in the simulator at least, a single channel autopilot autoland does a quite smooth touchdown. On single channel the 400 ft wind back of the stabiliser trim does not occur. Again from observations in the simulator a well executed (in other words, safe) manual go-around on all engines in IMC in the 737 varies greatly with pilot skill and competence. Some really botch it up while other pilots know exactly what they are doing.
What does sometimes happen on a go-around in IMC and which has caused grief in the simulator, is inadvertent premature flap retraction by the PNF without being asked. The PF is busy flying on instruments and not keeping a close eye on monitoring the flap position indicator. For example the PNF selecting Flap 1 inadvertently rather than flap 15 at the instant of power application on an all engines GA.
Now pitch up to 15-25 degrees caused by the strong nose up trim change with underslung engines at high power, and couple that with some pilots blind adherence to the flight director needles instead of proper cross reference to airspeed, attitude, altimeter and IVSI. Believe me with an incompetent instrument pilot it doesn't take long for things to rapidly get out of hand.
I have seen that happen countless times during simulator training to the point of stick shaker application. When that happens an incompetent pilot can make grossly over-controlled pitch down movements in fright and next minute the aircraft is seriously diving. It is all to do with lack of instrument flying skill in manual IMC flight. Surprisingly common. Thank goodness for flight simulators
