This is an extreme close up of a branch on a Smoke Bush.
Rather than overlapping 25% from one source image to another which is all that’s required if you’re shooting a landscape, when the iPhone is this close to the subject, you need to increase the overlap dramatically, to somewhere between 50 & 75%. If you toggle through the source images in Preview mode, you’ll see how heavy the overlap becomes in the last three source images, since they are closest to the camera.
In all fairness, this is more a “compound” image than a traditional panorama. But the principal is the same: the nodal point of the lens needs to be aligned with the center axis of the tripod, which requires a Gymbl. The closer you get to a subject, the more critically this principal comes into play.