Look again; it doesn't mix presentation and (business) logic. Unfortunately, the example from the tweet really does: the storage and manipulation of the to-do

Look again; it doesn't mix presentation and (business) logic. Unfortunately, the example from the tweet really does: the storage and manipulation of the to-do list itself is right there, mixed in with the rendering component. I think it’s a bad example of how to write UI code using React, because while it’s concise and it works, the techniques it shows lack flexibility and don’t scale well, and they’re not how you’d actually write a larger app’s UI that renders using React.