Not only beginners. I work with large teams with almost only seniors (10+ years of programming job experience) for large corps who don't know what 4nf is; they just chuck stuff in a table, update the same data across multiple tables, don't use indices or cascading rules etc. Everything is in code; the db just stores it, badly. They threat everything like it's mongo and this doesn't even work in mongo (no indices and it dies as well of course).

4NF was explained confusingly because it's quite complex theory. The fact the author says 'to be best of his understanding' it is 4nf is kind of telling.

With many things in software dev; it all doesn't matter until it matter. With few records and few users, like the average department LoB crud thing, it's not really a problem; it will be when either or both grow. My 'colleagues' (I am external) claim to know all this stuff, but in reality there is no proof they do; I have never seen them do things correctly with respect to dbs or software in general. That makes me a lot of money, but it is depressing really.