in camera view ,choose ‘project from view’,the aspect ratio of faces changes in the uv editor.
Have a square camera resolution or after you have unwrapped add a texture with the same aspect ratio as your render resolution. A UV tile is square but your camera is most likely not square, hence the distortion.
If I unwrap at first, then add a texture with the same aspect ratio as render resolution, the aspect ratio doesn’t change.But if I add the same texture at first, then unwrap ‘project from view’, the aspect ratio changes.