Can node-red node/flow run in parallel?

So what is the problem with the pattern as they describe? It shows how to split a flow into two separate branches and then recombine the result. It is true to say if both of those functions are entirely synchronous in what they do, one will run before the other. But imagine if each branch did an HTTP Request or database request - in that case both branches would be able to make progress whilst the other did async work.