Miles is revealed as an idiot from the second he admits to not being the one who created the boxes, his weird way with words, and the reveal he did not put the murder mystery together. Everything about him is pugnacious and despicable and it's only rhe absolute spectacle of the island (and the sycophantic behaviour of the guests) that brightens his dimwits for barely an hour of the screen time. That is not a twist. It's a sad revelation to a foregone conclusion. Like Brendan finding Emily dead in a sewer.