Spiky-head, Multi-branch, Blooming Yucca (Elata/Soaptree)

This is one rare article that I'm not totally convinced of my subject's ID. The 3-tile composite image shows an entire multiple-branch plant and enlargements of two prominent features—end of a branch with leaves radiating out from the center (rosette), and one of the bloom stalks. Read the entire article and comment there, please.