For me, I see hot yoga as a distinct lineage from Calcutta, that of Bishnu Ghosh (Bikram’s teacher), and encompasses more that 26 postures and a rigid sequence. This post might help explain what I mean:
http://lindsayfields.com/2009/11/27/what-is-hot-yoga-and-how-is-it-different-from-other-yoga-styles/
Good question!