When just using the defaults key, the types are correctly assumed. But when you add a schema it makes everything unknown. As you can see in the following screenshot, my code errors because Property 'width' does not exist on type '{}'. when using a schema, but it works fine when not. It causes the .get function to return unknown and the template type of the store becomes [key]: unknown. (This happens even if you have defaults along with schema, I just removed it so it would fit into one screenshot)

Another weird thing you can see in the screenshot is that the return value of .get() is an object that has any of the objects keys (but not any that aren't part of the objects) when the param passed into .get doesn't exist.