System Information
Operating system: Windows 10
Graphics card: GTX 1070

Blender Version
Broken:
2.80 Beta, 925380050d0, blender2.8, 2018-12-02

Short description of error
A subdivision modifier with simple mode distorts the uv map of its object. No problem with catmull-clark mode.

Exact steps for others to reproduce the error

1. Open attached .blend file
2. Switch on subdivision modifier of plane. -> UV gets distorted