Act I is the Introduction, also known as the exposition. Here we are introduced to the “normal world.” Now, the normal world may exist in a far future on an interstellar starship, or it may be set in a suburban ranch house with a swing set in the back yard, but the audience will give us great latitude as we establish the definition of “normal.” In this act, we learn the rules that govern this world, and something about the characters that inhabit it. In the Hegelian dialectic, this is the “thesis.” Act II is the Conflict. This conflict is introduced through an “inciting incident,” an act that disrupts the normal world outlined in act I. The tension introduced during this incident grows throughout the second act. In the Hegelian dialectic, the second act is the “antithesis.” Act III is the Resolution. The conflict is resolved, and the world and the characters in it are revealed to have been changed. In the Hegelian dialectic, the third act is the “synthesis.”
This also fits the logic of essay/article writing. I think the author forgot to mention that logical structure also contributes to the tension in writings as an important role. You should write something understandable with the tension to attract audience/keep them focused/ask questions spontaneously.