Every slide is smaller than a desktop stage, in a spread of aspect ratios, so nothing here should ever scale up past its natural size. Open one and watch the readout: the fitted box must follow the slide, and actual-size zoom must stay at 1 whenever the image is already shown at (or below) its natural size — a double tap on those is a no-op by design.
default (zoom + thumbnails) actualSize off zoomFromOrigin off infiniteZoom on back to the scenarios
open a slide…