I think the point the blog makes is that it’s important to highlight to children that computers have no understanding of what their inputs or outputs are. For example, an Alexa can tell jokes when you instruct it to do so, but an Alexa can’t find jokes funny.
And you’re right, people don’t create jokes or art from nothing. But for people, the process of creating a joke or an artwork is very different to that of an AI system. For people, it involves understanding and intention, and it’s an act of communication. People have a sense of acting in the world. AI systems don’t.

how many humans actually “create jokes” compared to the number of people who hear jokes and then tell them again just like Alexa? Same for artwork, no humans ever create artwork ex nihilo, the tools used have been designed by someone else, and countless influences are part of the artist’s inspiration, how is this different? John Coltrane did not invent the saxophone or the major and minor scales. That’s what “standing on the shoulders of giants” mean.