this isn't really accurate IMO, from the start when he says 2d flatlanders can only see 2 dimensions.
In fact if you were 2 dimensional you would only be able to see one dimension, so with the example of the balloon the 2d flatlander would just see a line getting longer then shorter.
Similarly, we can only really see in 2 dimensions, we just see in 2 dimensions twice (once with each eye), and extrapolate from that. We can move in three dimensions, but if we could see in 3 dimensions we would be able to see things behind other things
edit: i havent finished the video yet but yeah once the guy gets to the fifth dimension it's basically just meaningless word gymnastics