This bug does exist, as shown in the video:
After uploading the image, a prompt indicates that a 64x64, 64x32, or 128x128 PNG file is required. The uploaded image is 64x64 (specific parameters as shown in the image) and in PNG format. The platform is Android 9. Tests have confirmed that all 64x64 skins cannot be uploaded (other sizes have not been tested; the bug is reproducible).
pictures here