I too had never heard of the "polytheistic Judaism" that Dorkman spoke of. However, after listening to the video, I saw what he was talking about, and started laughing. This isn't anything new to Christianity or Judaism, Jehovah, Yahwey, Elohim, etc aren't seen as different gods, but as the same god manifesting himself in different ways.
Which is a bit like responding to the Secret History of Star Wars with "Oh, no, you see that's explained in the Young Jedi Knights series, that when they referred to this, they were actually referring to that."
The point of the video is that they were seen as different gods for centuries, per archaeological and anthropological evidence, until the concept of monotheism was invented, at which point they were retconned into a single god with the explanation you've just given.
You missed the point of the video completely. High five.
Although you're right that this isn't "new" to those religions -- it predates them and forms their foundation.