Is there a reason why the incision line (for double eyelid surgery) is not where the crease fold occurs?

It is indeed true that the incision line and the eyelid crease might not align exactly due to the dynamic nature of eyelid structures and the way skin stretches and heals. The eyelid is a complex, moving part of the body, so the positioning of the crease post-surgery can vary slightly from the incision line. However, generally, these two should be close to each other for a natural look.

My personal preference is to have the lateral part of the incision align closer to the crease because of how the natural eye contour slopes down naturally towards the lateral ends, which would create visible flaring at the lateral ends of the incisions if the incision is placed too high. It's important to communicate your aesthetic preferences and concerns with your surgeon, as they can tailor the surgical technique to meet your specific needs and desired outcomes.