It's mostly this thread where it matters, anyway. At 20 reviews, the top and bottom 5 or 10% only affect ratings by very small fractions. Certainly not enough to entice or deter someone from visiting a course. So it's the minor issue of who makes the "Top 10" list, and the very minor issue of which order they're in. Hardly worth changing the formula for 5000 courses just for that dozen or so.