Not sure if this is an issue with the PinchArea itself, or the example
code here

examples/declarative/touchinteraction/pincharea

Running that code, pinching in and out the image scales in and out an
equal amount. But if you anti-pinch to zoom in, then release your fingers
from the touch screen, and start a new pinch-together, the pinch distance
required to zoom out again is a lot bigger than what was needed to zoom
in that same amount.