It's a thread running through the article that the big thing about merge is that it is hierarchical and not sequential. e.g., see the following passage from the article:

>> [Merge] applies to discrete units of language (words or their parts). It combines these, not sequentially, but hierarchically.

Or the paragraph at the start where human language abilities are contrasted to bonobos' and chimpanzees' and deep learning models' sequential processing; etc.

My knowledge of Lisp is rusty, but as far as I remember it cons is a list operator that joins the head to the tail of a list (like the "|" in Prolog). So it imposes an order - on a sequence. Apologies if I misremember this.