I'm not sure what you mean about Merge being non-sequential. All Merge does is take two elements α and β, then return a binary branching structure with α as the head, like so:

{α, β}

Both α and β can be either some atomic unit, eg a word or a morpheme, or the previous output of Merge (a tree).

This is their first example as rendered as cons:

(cons I (cons drink wine))

As merge:

{ I, { drink, wine } }

As a tree:

Edit: I can't get the tree to look even remotely correct in HN formatting, but you get the idea. It's in the article.