I think of this as the musical movement of the story and the broadest application of cause and effect.
Like musical movements, each creates a different space and mood.
The MC sees the IC as an annoyance in Act 1, what changes to make him useful in Act 2, a friend in Act 3, a man apart in Act 4?
This is true of every Act/Throughline, in my opinion. You should 'hear' the difference, and feel it. It's a benchmark, a measure of change, and is one of the main things that gets the readers/viewers attention, and keeps them involved in the story. "Oh, look, he thinks differently now...oh, I see why..."
The MC is conceiving how to deal with his new relationship with the IC. from the perspective of the PSR Universe Quad, he seems to be annoying, possibly because the IC isn't matching what the MC is conceiving. There's a space between the two.
The MC is observing the Psychology of the situation, probably figuring out how to get the IC to match his expectations.
The Universe concerns are affecting the psychology. This is the PSR Twist, the introduction of the second element that alters the course of the plot. If there was Equality there would be no conflict and no story.
"Annoyance" answers the question "How is the MC conceiving of the IC"
The IC's behavior comes out of his own Conceiving, not matched to the MC's.
The MC and the IC are settling in and Being, and now the MC is seeing the IC's value and how he might think of him as being useful, just as he is. There is how the MC perceives his being and how the IC perceives his Being, and also how the actually are Being, and the two are not matched, once again. The IC may or may not be useful, or be willing to be useful.
The MC is observing the Psychology of the situation, probably figuring out how to get the IC to match his expectations of Being. He's having guests over, he wishes the IC would pick up, get out of his gym clothes and put on something decent, take a shower, dress for company.
The Universe concerns are affecting the psychology. This is the PSR Twist, the introduction of the second element that alters the course of the plot. If there was Equality there would be no conflict and no story. If they were exactly alike in their Being, they would be Felix and Felix or Oscar and Oscar.
"Useful" answers the question "How does the MC see the Being of the IC."
The IC's behavior comes out of his own Being, not matched to the MC's.
Because of the Conflict around Being, one of them is now Changing and Becoming; either the MC is Becoming and so his perspective on the IC changes, or the IC is Becoming and the MC notices it, although his perspective is unchanged. Because they have found some alignment of Equality they can possibly think of each other as friends, meaning that they care about each other's comfort and problems. But they may not work out as friends, and even if one of them sees the other as friends, the other may not; or they may see each other as friends at different times and never connect.
The MC is observing the Psychology of the situation, probably figuring out how to get the IC to change in the direction that the MC wants him to change in. If he's changing in a different direction, that creates conflict, but it doesn't mean they can't be friends.
more to come...
The attempt at thinking of each other as friends either fails or runs its course.
In the IC throughline of Psychology it's what the IC is thinking, seen probably through his behavior as well as his dialogue, and what the MC thinks of what he's thinking.
This all is centered around the IC solving his problem and pursuing his desire, and the MC observing it.
(more to come...)