And I'm in disbelief that you think they're different. Cloud is not himself, him playing a fake persona is more than just him pretending, or at least that's always how it's been presented. His mannerisms actually change, his memory actually changes, HE actually changes.They are definitely, definitely not the same thing. Cloud having delusions caused by grief is mental health issues... Cloud being possessed by Sephiroths is where the fantasy element comes in. I'm not 'playing favourites' I'm using my brain. Cloud not coping with Zacks death and dissociating from reality is not the same as being possessed by Jenova cells. When Cloud takes on Zacks persona he is still himself. When Cloud is possessed by Sephiroths Will he is not even remotely himself. Cloud being enamored with Aerith and thinking he's in soldier is not comparable to Cloud being literally possessed and violently attacking Tifa or Aerith or whatever.
Like I'm not gonna lie.. I'm literally in disbelief that you're comparing those two things. Heck.
Jenova taking "direct" control is just more direct and harder to resist, it feels different because it's less subtle and we as humans have a bias where are very tempted to see people as a sort of concrete thing where the only time you are not at fault for punching someone is when your hands are literally being pushing into them by someone else. It's an uncomfortable truth, but truth nonetheless. It's because people are desperate to hold on to the notion of free will so they can assign blame, they like things in neat boxes with no grey areas, let alone gradients, they want clear and uncontroversial agency, makes the world a simpler place.
But what if the reason you punched someone was because you have a malignant tumor pressing on your brain causing you to release different hormones than usual, Is that you? It literally is, they're your cells. What if someone injects you with a drug that induces rage? What if someone forces you to stay awake for days on end while constantly prodding you, causing your brain to essentially go haywire? Is that still you?
The answer to those things is always the same, "things are what they are, and the rest is semantics", what really matters is how your actions reflect on you as a person, whether the actions say something about how you will act in the future, how safe you are to be around, etc.
Cloud, in his Soldier Persona, is acting in a way that is different from the way Cloud in his natural state would behave, not just because he's going through trauma (which honestly would already count as an outside force, which is why we call them "mental illnesses" rather than just "personalities") but because his memories and behaviors have been literally rewritten.
For more proof that it's the same just look at Cloud attacking Aerith in the City of the ancients in the OG, he stopped himself, clearly he COULD stop himself, which means his hands weren't literally being held, he was just influenced more strongly than normal.