Often when writing you need to make decisions as to how to get through the different points you need to inform the reader about, if you are writing a jocular, breezy piece you will choose different strategies than otherwise.

The joke, such as it is, is clarified by what follows:

Back in 2012, I had not yet been born (I am, in fact, only six years old). But I am a student of history.

How does that clarify - because the student of history thing indicates now he will need to give us some background of things that happened a long time ago. Of course it didn't happen a long time ago, only 6 years ago, but there is the concept of internet time going faster than normal time. In fact it seems a really long time ago to anyone paying attention that Cook had to apologize - oh remember when that happened.

So he makes a joke that gives us a light feel and that also points out in a roundabout way hey it feels a long time ago but was only 6 years but bringing it up seems like ancient history without having to directly reference the hoary old trope that internet time is happening so fast that 6 years feels like ancient history man!

Anyway, often people writing things, especially if they have a deadline by which they wish to be finished, and especially in our modern era when there is not enough editing (remember editors, boy internet time really wiped out that species!) end up writing things that are allowed to remain in the article even if they are significantly less successful than other things.

I’m the Mozart of Mappy Think Pieces

It is a joke.

An simple outlandish claim doesn't make constitute a joke unless it's referencing something. I think that reference is what GP is asking about.

Sure it does, such a joke is often called absurdist or surrealist humor. Quite popular on Twitter.

Anyway, I think that is a lot more likely than some obscure cultural reference that we’re expected to parse in the middle of musing about digital mapping.

No, it’s clearly a joke - it made me laugh! It doesn’t need another reference point because the claim’s very existence is a reference to people’s reticence to admit their own age (due to vanity) or fear (of facing one’s mortality). That has been a common point of humor for ages (pun also intended).

As bizarre as this may sound to your generation there are, in fact, such things as standalone jokes.

I honestly don’t even know what generation you’re assuming I’m from and referring to. Is this supposed to be something old people don’t understand? Or young people?

Of course you can have standalone jokes, but “I’m six years old” is not one.

It’s not a generation thing. The joke is the OP is obviously not six. We know that because most six year olds can’t come up with such an artifact to set the timeframe of an article. For more references on jokes like this read MAD. ;)

Could you give an example? Even puns stand on aspects of language to acquire their potency.

Then it definitely is not that funny of a joke. He could've added "and I am 10 meters tall" without affecting how funny his joke is

A joke doesn’t have to be good... most aren’t!