The splash page will only work for the front page method.
I made a note to look into adding a video splash page option for an update. I will do that this week to see how one will work for this theme–hopefully, you are not in a big rush as this might take a bit of time to implement if I add one. At the moment, I am finishing up on a new theme release.
I will look online and other themes that allow video splash pages; better if it can be done without a plugin. For this theme, I think I would do it as a page template.
Are you using the classic or block editor?