I suspect they used US customary units because that's what's used in the video.
Anyway, if we're only going to talk about readability then I'll note that the text is imminently comprehensible to anyone with an intuitive grasp of said units. So the real question is one of functionality. (I'll put my vote in for metric, of course.)
For people using A4 paper: The long side of A4 is 297 mm. So one billion bits of A4 (plus another one billion bits of 2.792458 mm) are how far light travels in one second.
The distance travelled by light in 1 ns, = 299.792458 mm (11.803~ in).