Much as I sympathise with the idea that you must train and test to do exactly what you would do in real life, it is not possible, especially in SPIFR helicopters.
In testing (for the IRT or OPC/LPC) you have to have a point against which you can assess the candidate, but that point has to have a tolerance, hence the DA +50', -0' Standards Document 28 is not a training document, it is essentially a list of markers against which to assess a candidates proficiency.
In testing the candidate is in a FSTD, in which case he "knows" he will never see the ground unless the examiner has set the WX incorrectly! Or, he is in a helicopter with some form of artificial "blind flying" system, screens or glasses/hood etc. As an examiner you must see that he can fly an approach and knows the limits to which he can operate the helicopter, theoretically and practically.
In real life you are going to have the aircraft setup to fly the approach and be able to take in peripheral cues as they arrive, a flash of the surface in the chin bubble etc and when you see these cues you are going to be flicking your eyes back and fore between the instruments and the outside world until as you arrive at DA you more or less already know what is likely to happen. If you have seen only grey, soft cloud type stuff, you will be going around. If the flashes of surface have become longer and more distinct, you are looking to get those required visual references at DA that will allow you to continue the approach. Remember this is SPIFR, the pilot has to do everything and that includes looking out! So unless the chin bubble is clear of cloud but the cabin still in it, you are likely to be in a good position to make a sensible decision.
A word on what to do and say at DA when being tested, dont bother with "Decision, looking up, nothing seen, going around" - JUST DO IT! If you initiate the go-around at (or within +50') the examiner will pass you. If you initiate the go-around below DA (-0') because you talked for 3 seconds, he will fail you. You only have to tell ATC when you are going around, because they cannot tell when you pull pitch, the examiner can!