>>3040052The "selfie" camera on most phones has a wider field of view than the rear camera, because it needs to capture your whole face even when used relatively close-up. But the wider your field of view, the more distorted an image you make.
The exaggerated features you're talking about are typical of photos taken with wide-angle lenses, which is the reason portrait photographers use long lenses to make their subjects look good - and why Diane Arbus used a wide lens to make her subjects look stranger and more grotesque, as in the attached picture.