Is there a specific industry accepted reason that the Confidence Interval defaults to a factor between 60%-65%?

The distribution of losses in a confidence interval generally follow the shape of a lognormal curve. Unlike a normal curve, the mean of a lognormal curve will almost always fall to the right of the median. While a normal curve would have a mean at 50%, a lognormal curve’s mean is usually greater than 50% due to the tail to the right. The amount that the lognormal mean is greater than 50% varies based upon the standard deviation, but it generally falls between 55%-65% for most loss projections.