Bike seat height adjustments are very simple: the seat is mounted on a tube, which fits within the slightly larger seat tube and then is clamped.
Getting the exact same position is easy: just use a Sharpie marker on the inner tube to show where it fits in the outer tube. Draw a second, vertical line across both tubes to make sure the orientation is the same.
Yeah, but if you do that before a race... someone's going to do it quickly and not do a great job. Like I said, it's not that difficult to detect a difference of a few millimeters, and it's annoying.
Getting the exact same position is easy: just use a Sharpie marker on the inner tube to show where it fits in the outer tube. Draw a second, vertical line across both tubes to make sure the orientation is the same.