Software is hard to make secure.

That is, to verify it does what it says it will do and what the user expects it to do.

Apps, which by necessity have a larger audience, can be audited or verified not to be doing something sketchy by their more savvy users.

But what about an app that was just hallucinated on the spot just for you?

No one else has seen it.

If someone tricked you in creating it, it could do nasty things.

Hallucinated micro-apps need a trust model where the individual micro-app doesn't have to be trusted.