My take on this, I fit a boiler last week which was about two metres from a door. I turned the flue terminal to point away from the door and away from the garden path. The trainee I had with me asked why when the flue was about 2.4mts high and I said just because it's good plume management. It reduces the risk of POC blowing back in, and it stops anyone from walking up the garden path getting a face full of POC/steam. I personally wouldn't ID a boiler for this but would offer strong advice and insist on a plume management kit.