I'm 99 percent sure that wasn't hian's point at all, but I'll leave that to him.
How not? The argument was about why Cloud failed the get into SOLDIER. hian felt that Cloud's true strength lies when he is doing things for more then his self-interest. And serving a corrupt, greedy, oppressive, fascist corporation that strips it's employees of it's free will doesn't work for that. But true or not Cloud probably didn't believe any of these things when he was applying to SOLDIER so it shouldn't matter towards the success or failure of his application. And if these facts about Shinra should have been perfectly evident too 14-year old Cloud then asking why it didn't work that way for 14-year old Zack, who also wanted to be a hero and is at least just as selfless as Cloud, is a valid question.
But hian never said anything about "these facts about Shinra should have been perfectly evident to 14-year-old Cloud." He explained the argument he was making (very clearly if you ask me), and addressed that question about Zack (and every other Shin-Ra employee) while doing so:
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"I've always gotten the impression that Cloud not making it in Soldier was a specific narrative device playing into the 'people are only strong when they fight for what they believe in/other people' trope that is so common in Japanese shonen media.
Cloud is clearly strong enough to do nearly impossible feats when he's doing it for the sake of other people (surviving the fall from Mt.Nibel searching for Tifa as a child with only a few scratches, or beating Sephiroth in the Nibelheim incident, or at the end of the game), whilst young Cloud joining Soldier was doing it purely out of self-interest.
So, I think it's strongly thematically implied that Cloud fails Soldier because he doesn't cut it, and the reason he doesn't cut it is because he can't realize his potential in pursuit of self-interest (which is an extremely typical Japanese way of thinking)."
"Finally comparing Cloud to other Shinra employees is completely inane in this context. The lesson isn't that 'people can't join Shinra and Soldier out of self-interest', which they clearly can.
The lesson is 'Cloud, who is the main character and probably the strongest character in the FF7 universe, can only bring out that power for the sake of other people' which furthers the theme of collectivism and solidarity which is common in Japan.
Ultimately, Shinra loses, and ultimately everyone who were in it only for their own sakes lost out in the end of the game.
Cloud not making it within that morally bankrupt and selfish system despite being stronger than the strongest of the soldiers within it is a moral statement on part of the writers."
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This is framed as a literary analysis, not an in-universe discussion. Zack or whoever else can be as strong as their stories call for them to be regardless of their knowledge of Shin-Ra's activities because different themes are at work with them than what was going on with Cloud's personal story.
If you find this an unsatisfactory answer, it's because you and hian are discussing two different things.
For the record, the closest he said to what you're saying he meant was "Cloud would not have been able to manifest or prove that strength in the environment of Soldier, since they'd never have him fight for things that actually matter to him" -- which is still not saying anything close to "these facts about Shinra should have been perfectly evident to 14-year-old Cloud."
Remember, what he was talking about is how a theme took form within the story.
Minato said:
That doesn't answer the question: How were they more involved than Cloud?
They were all in Tifa's room (the first day Cloud was there). They all went to the mountain. Only Cloud and Tifa were there when they fell.
Cloud wasn't in Tifa's room, he was outside. Tifa, in her room, tells these other children that she wants to see her mother and they decide to go up the dangerous mountain, Cloud follows in their wake. They ditch Tifa halfway up the mountain. After Tifa's fall she goes into a coma, Cloud is blamed for the whole thing, the adults not knowing anyone else was involved at all. And after Tifa wakes up she doesn't remember any of it and no one tells her about for the next 9 years.
The point is made that it was the first time Cloud was in her room, and she hadn't even realized it. Cloud's subconscious explicitly tells Tifa:
Tifa: "My room?"
Cloud: "It was my first time there."
Tifa: "Was... it?"
Cloud: "I only used to look up at it from outside."
Cue the flashback of little Cloud approaching Tifa's house, one of the other kids asking Tifa "You think he wants to come in?" and then little Cloud walking "downward" (on the screen) out of view of the window, meaning he walked to the door and came in.
Tifa then asks "Was that the first time you came into my room?"
This strikes me as fairly straightforward.
Minato said:
So saying Cloud is equally immature for not liking the guys that let him take the fall and never tell Tifa in all the years they are friends as much as these kids are for not liking the kid they know is disliked by the rest of village for at least somewhat inaccurate reasons, something they don't have the courage to even put into a letter, much tell Tifa about directly doesn't hold up. They're all immature but saying everything is equal and mutual between them is unfair, Cloud has sound reasons based in reality for his negative opinions.
They're all immature, yes, and the other kids should have spoken up. My point was that they weren't there when Cloud and Tifa fell, so they ultimately didn't know why she fell. All they would have known is that their friend was in a coma, all the adults in their world were blaming Cloud for it, and Cloud himself suddenly took to being a little shit who was trying to beat them up.
They were all kids. None of them were criminal masterminds.