How to check?
1) Set Rendered mode for 3d View
2) Set "Blend Sky" and "Real Sky" flags for world.
Rotate view you will see right color blending from Horizon to Zenith color.
3) Add environment texture
Rotate view and you will see incorrect texture mapping that is not correspond to color blending that was observed in previous step.
So I conclude that this is a bug.
This issue must be solved before the patch D1414 because BI behavior is the viewport target.
Example: {F273051}
Alexander (Blend4Web Team)
Reviewers: sergey
Reviewed By: sergey
Subscribers: Evgeny_Rodygin, AlexKowel, yurikovelenov
Differential Revision: https://developer.blender.org/D1729