I must be careful not to try and speak for McGrath - which he can do perfectly well himself - but I think I know what he's getting at. I see the truth as being what you try to get over in the song. It doesn't necessarily have to be a moral or a conclusion - just the big picture. The facts are the exact details - which can often contradict the big picture. In any form of writing, you will have to select the facts/information/details which you give. You don't have time to tell the audience everything. When I try to tell a story. I pick out the "facts" which I think best support the story which I'm trying to get across. Hope this make sense.
I have an open mind about listening to other songs on the same event. At the end of the day, I would be looking for my own angle on it. I don't know whether listening to other songs would help or hinder the process.