Setting the r.ScreenPercentageTranslucency Variable below 100 causes Texture Swimming

When setting the 'r.SeparateTranslucencyScreenPercentage' variable to any value other than 100, UV world space textures begin to swim. In the example project attached, I created a simple translucent material using the Noise node connected into the opacity input.

I then placed it on the default floor mesh and entered 'r.SeparateTranslucencyScreenPercentage 50'. The texture immediately began to swim.

This variable was added into the 4.11 release, so this is not a regression as the setting did not exist prior to this engine version.

Note I've found there is a solution to this issue, by unchecking the 'Separate Translucency' option within the material editor itself, but I do not know enough about this new variable to say if it disables the screen percentage as well.

1. Open attached project.
2. Bring up console command (~) and type 'r.SeparateTranslucencyScreenPercentage 50'

Outcome The noise textures on the floor begin to shift and swim.

Expected I would expect no behavior change in the material, but just the screen percentage value being set for any materials using separate translucency.