As long as the goalposts can keep moving, the experiment can continue. If the goalposts stay still for too long, common sense creeps in and lots of people notice that it's mad to experiment on children given what's at stake for their future mental and physical health.
Moving them around creates just enough confusion for just enough decision makers to say that they back the trial, even if they feel uncomfortable. Some don't feel uncomfortable at all and seem oblivious to the goalposts moving. Others will be actively moving them.
For clarity, my comment is about goalposts moving around in general. The PP who is making comments where the net effect is that the goalposts have moved may not be aware that this is what's happening here. Equally, they might. Either way, the goalposts have moved and it's helpful to have it in this thread.
Question to @Tottenhamhotflushes : do you agree that the goalposts moved in the way Aims described?