I've got no skin in the game either way, but if there is a requirement to consult before a trial, then the overwhelming response will be negative. Human nature dictates very few people will welcome aircraft flying overhead them when none (or at least fewer) have before.
So if airport X consults on, for example, an RNAV departure trial, and 95% of respondants are negative, what happens? No trial? But maybe the CAA permits it anyway, due to the value of the trial to future developments, and then the community feels even more disenfranchised because of this.
I'm not sure of the "full" - but if the airport wants to maintain any level of trust with the local communities and a sense of a social licence to operate it needs to have a meaningful engagement with the people it is going to affect in advance of inflicting significant changes from trial procedures.
I think this is what did happen with OF trials, but as I said Heathrow were receiving noise complaints specifically referencing Operation Freedom trials months in advance of them actually happening. As you say, perceived noise/annoyance is often very different to actual noise levels, but the 'engagement' by the airport can heighten that perception of noise without any changes taking place.
It's not an easy situation to navigate.