Can you judge someone’s identity from a photo that may be stretched?

Not much from a reposted image by itself. Cropping, resizing, camera angle, and perspective can all change how someone looks. Before comparing people, you would want the original image and reliable information about how it was captured and handled.

Build or facial resemblance is subjective, especially in a single still. A visual impression can raise a question, but it does not establish who is pictured or how the image was used in a case. That takes more context than a side-by-side comparison.