Originally Posted by
rpenmanparker
Setback means perfectly horizontal distance. That's all the rider cares about.
Yes, from the bike or global point of view. But we're comparing seat posts, and need to have common language about that. This rider, the OP cared about what seatpost should he buy, and whether the Ultegra he found is likely to have enough setback.
There's a reason for talking about measurement.