Why does Gayfeather (Liatris) bloom from top down?

Question

Most every plant with a flower stalk booms from bottom up. Why is Gayfeather different. There has to be some botanical explanation.

Answer 1

I consulted several sources and didn't see any explanation as to why they open from the top down other that they do. It appears that all varieties of liatris do open from the top down.
Here is a photographic article, that further shows the flowers open on one side first.

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artsep09/bj-liatris.html

This article says that blooming from the top down extends the flowering period:
https://plants.usda.gov/plantguide/pdf/pg_lipy.pdf

Here is general information:

https://www.gardeningknowhow.com/ornamental/flowers/liatris/liatris-blazing-star.htm