Source Textures used with a Rect Light are blurry and diffused

This is a regression from 5.0.3 tested in the following streams:

The source texture lighting appears to be rendering incorrectly when compared to the previous release.

1. Create or open any project
2. Place a Rect Light in the scene so that its lighting can be seen easily
3. Set the Source Texture of the Rect Light to a texture with clear markings(Default Calibration texture in Engine Materials works great)
4. Observe the Rect Light's light

Expected Results:
The lights are clear and match the source texture.

Actual Results:
The lights are blurry and diffused.