HTML5 Dynamic Shadows work? What? Need some help understanding...

Looking at it tells me that Directional Light with Mobility = Stationary is the highest possible directional light you can use and if you want Dynamic Shadows to be cast you need to use Stationary with Cast Modulated Shadows.
So while exploring the rendering limitations I came upon something strange that I would like to understand.

I have these objects in my scene:
Direction Light. Mobility = Movable, Cast Dynamic Shadows = true, Cast Static Shadows = false, Cast Modulated Shadows = false
StaticMeshActor. Mobility = Movable, Dynamic Shadow = true, Static Shadow = false
SkeletalMeshActor. Dynamic Shadow = true

Now the way the documentation describes the limitations, you would now expect the DirectionLight to not light anything properly and the StaticMeshActor and SkeletalMeshActor to not cast any shadows.
First off, I’m using the Preview Rendering Level set to Default Mobile / HTML5 Preview which sets my editor viewed Feature Level to ES2. Now in both the editor preview AND the launched project in browser I have lighted objects throwing down dynamic shadows. How is this possible? I looked through the 4.8, 4.9 and 4.10 release notes and nothing states a feature like this. So I’m wondering if the Directional Light is automatically set to Stationary behind the scenes if its set to Movable? And if Dynamic Shadows is selected it automatically turns on Cast Modulated Shadows?

Can anyone provide some kind of insight? It’s really hard trying to develop for a platform if the settings don’t behave as documented or expected.

Ok I just found why this is, in the engine 4.5 release notes there is one sentance:

Seriously, the docs need updated. This is mentioned NOWHERE except there. Unreal Engine 4.5 Release Notes | Unreal Engine Documentation

Very helpful just to know about that trick of switching the light to Moveable to make dynamic shadows work!