One of the first things they stressed was that they're now using HTML5 and that it's providing them with larger draw distances, dynamic shadows, higher resolution textures, and other graphical improvements. Now, correct me if I'm wrong but all of these improvements could've been achieved in Java through LWJGL. It kind of annoys me that they're heralding HTML5 as enabling these things when it can already be done on their current platform.
It looks to me like a simple case of corporate speech. The way it works is roughly as follows:
1. A decision is made that to keep up with expectations, the game needs a major frontend overhaul.
2. The possibility of doing it in HTML5 is suggested, and after various considerations are weighed the decision is made that the new frontend will be in HTML5.
3. Because most people aren't pedants and the project is a topic of daily conversation over months, "the new frontend, which happens to be implemented in HTML5" is abbreviated to "HTML5". ("How's HTML5 coming along?")
4. People forget that it's an insider term and use it in videos for public consumption.
(For what it's worth, all of those improvements were technically possible in the software rendered version. Of course, letting the graphics card do the work gives a better frame-rate, but you can see dynamic shadows in Torquing!)