HTML still requires Flash?

I just published a course in Storyline 2 to my LMS and selected 'include HTML output' when publishing.  When I did a preview of the course in my LMS, the course window came up with the menu and title bar, but no content.  After playing around with it, I enabled Flash and it worked. 

I only know enough to be dangerous, but one of the main reasons I  switched to Storyline from another content development software was my (apparently erroneous) understanding that HTML output would bypass Flash problems for learners.

Can someone dumb down for me why Flash needs to be enabled for course viewing that was published with HTML output?