If you actually were trying to get collisions, you'd save all previously generated ids and check all of them for a match with the newest one.
Not only would this increase the chance of a collision (not enough that it should matter, but still), but it would more closely approximate a real use case - if you use UUIDs you're not just in trouble if two consecutive ids are identical, it's usually a problem if any two ids are.
But the presented snippet is simpler and shorter and is close enough to what a naive test might look like, so it's well suited to getting the joke across.

The only way I could imagine this not being fake is if it was achieved in a noncompliant Js implementation. Which seems highly unlikely given the screenshot looks like the Chrome console.