You haven't found that out at all. You read that this could be their policy. But you certainly haven't read that they do that no matter what - changing conditions of a wet race make all that redundant.
A former McLaren mechanic has said that it was McLarens policy this weekend, GlenP knows he's wrong though.
I do say 'that's what we've heard', plus that's what I saw with my own two eyes across the entire race, you prefer the idea that Hamilton and his RE got every call wrong, cool.