Color me impressed. Even being very well versed in database design myself, this is just pragmatic and straight to the point, the way I'd have liked it back in the day.

I think the main problem of how 4NF and 5NF formal definitions were taught is that essentially common sense (which is mostly "sufficient" to understand 1NF-3NF) starts to slip away, and you start needing the mathematical background that Ed Codd (and others) had. And trying to avoid that is how those weird examples came up.