I think the case works better when you look at it from a variety of situations. Instead of two humans, what if one is a species that doesn't speak the same language? Or a mindless undead? There are likely more, but there are two popular thoughts on this.
First is that the mechanics need to make logical sense. Is it mind effecting? Is it a feint? The rules describe when it qualifies and how it works. The second type views it purely as a mechanical rule to determine fail or success state. How it works is however they say it does in any number of situations.
For example, the first may view CAGI as a mind effecting taunt. Works against a human, but not against an undead creature. The second, would simply say its a mind effecting taunt against a human, but a clever feint against an undead.
To be honest, why are we really even entertaining the first type? I mean this earnestly and not in an insulting way: the power itself doesn't mention any sort of specific method that it's using, it's not outlining a specific technique or making mention of any sort of specific in-universe mechanic to work, so why are we trying to
find one? It feels like it is missing the point of 4E's design.
To give an example, in PF2E the Demoralize action has a bunch of limitations, largely because it's
specifically outlined what is meant to be happening when you do that. You can do it in other ways, with penalties (or feats that take away those penalties), but the rules outline those limitations very clearly. And if you have problems with that, okay, that's something to discuss, because we can agree or disagree with how it's modeling it. But we can clearly see that the designers
intended to have specificity in how it works.
Here, we have the opposite: we do have flavor text, but there's no mention of limitations or specifics in the power's mechanics. Like a lot of 4E powers it's clearly meant to be open-ended so that it can't be preemptively DM-limited in some way like, say, against mindless undead if it were simply an insulting taunt. It's open-ended to give it as much applicability as possible, and you're free to come up with a variety of ways.
To me, the problem is that people are looking at 4E with a 3E mindset: 3E something that is built around very specific ideas, limitations, etc. These things can be bent, avoided, and even skipped, but 3E is typically built around specificity in how things work; It is concerned with
cause. Meanwhile we have 4E, which doesn't really care as much for how something it is done as much as
what it does; it is concerned with
effect.
Now there's nothing wrong with being more in-sync with 3E (or other, more specific/simulationist RPGs) mindset, but I don't really see that as a flaw of 4E. That feels more like the problem of the player, in the same way someone criticizing using clocks for enemies in BITD instead of hit points is missing the point of the design by trying to fit it into a box it's not meant to fit in. I feel like that's what is going on with CaGI so often: people try to put specificity on it and when they can't, they call it "magic mind control" because in D&D magic tends to be much more open-ended and interpretative when it comes to cause, which is largely missing here.