When expanding an Adobe Stock image in Adobe Stock AI Studio, and choosing BOTTOM-CENTER, the bottom of the original image gets cropped off instead of simply justifying the image to the bottom of the new canvas. Why?

When I find an Adobe Stock image I like, I take it into the AI Studio to expand it so that it fits my design needs. However, the app is cropping off the image top or bottom when I choose CENTER-TOP or CENTER-BOTTOM as the position for the portrait or square expand size instead of just moving the image up or down to the top or bottom edge of the new canvas. To avoid the cropping of the image, I have no choice but to use CENTER-CENTER, which give equal space above and below even though I do not want the image expanded on both. 

Why isn’t the AI just pulling/justifying the original image to the top or bottom edge of the new canvas? This seems so simple.