[JohnM]

Above 200Hz or so the gate time that approximates the way our ears work is about 5ms, which is to say that reflections inside 5ms tend to be perceived as part of the initial arrival and so their effect on the response colours our perception of that direct signal, whereas after 5ms the arrivals are perceived as distinct from the initial arrival and correcting for them would overall have a detrimental effect on the perceived balance.