I can’t tell if the scientists who make such statements are just trying to “dumb down” the physics for popular consumption, or if they really are that dumb. Announcements like that are paradoxical and incomprehensible.
Are we invited to imagine that we were floating outside the universe, (which is impossible, since the universe is everything), looking down on this cute little marble sized universe (again impossible), and we watch it explode to incomprehensible size in an incomprehensible instant?
Also, after the explosion we have to change our mental image and get back inside the universe somehow, in order to avoid being stranded outside the expanded universe, a lonesome transcendent God instead of an existent human being.
Scientists who think they are describing reality with their equations have become blind to their own humanity, so they don’t see the irony in their Godlike pronouncements.
The big bang is a mathematical singularity, an artifact of the equations that physicists use. It’s like starting with a hundred jellybeans and each day eating one. As soon as you understand that process, you realize that a hundred days from now, you will have zero jellybeans. It’s a mathematical result, an artifact of the human mind. It does not mean that today’s jellybeans do not exist because in a hundred days they will be gone.
In the same way, running an equation backward in time instead of into the future, it is an error in reasoning to say that today’s universe was once the size of a marble.