Reproduction steps:
1. Open the attached “IN-96472.zip” project
2. Open the “SampleScene”
3. Click on the “Image” GameObject from the Hierarchy
4. Observe the Image in the Scene or Game view

Expected result: The Image Sprite is fully white with no transparent borders
Actual result: The Image Sprite has a semi-transparent border

Reproducible with: 6000.0.9f1, 6000.0.41f1, 6000.1.0b9, 6000.2.0a6
Not reproducible with: 2022.3.59f1, 6000.0.8f1

Reproducible on: Windows 11, macOS 15.3 (M2 Pro) (user reported)
Not reproducible on: no other environment tested

Notes:
- Modifying “Pixels Per Unit” to a higher value for the “test_white.png” Texture sometimes would fix the issue (even if then reverted to the original value), but clicking “Reimport All” makes the issue reproduce again
- The position of the semi-transparent side(s) changes randomly depending on the atlas composition
- The issue reproduces with all Formats except for “RGBA 32 bit”
- Reproducible on a new project when creating a small white texture and packing it into a Sprite Atlas