Loading screen from Unity not working?

I'm currently working on a project with an interactive 3D model, where the user can rotate the model and hover or click on certain objects to show more information.  

I was able to get the application embedded into a Storyline slide with no problem, and previewing it in Review works great.

However, the model is fairly complicated, so it takes a few extra seconds to load before the custom splash screen comes up and the scene is visible.  I created a loading screen that works in standalone, but when it's uploaded to Review, it seems that it still wants to wait until the entire scene is actually loaded, before it plays, so the loading screen isn't even seen.

Is there something I might be missing in the HTML code that I embedded, a Storyline setting itself, or something else?  I feel pretty certain that my player settings in Unity are correct.