I don’t know if its a bug or not, but in Vray 2.0 for Maya, using Rt, if are using Cpu, Global Illumination activation is respected, while using Gpu, no matter if GI is on or off, Rt will show always On.
For my side, there is any problem with this, I suppose you’ve done this because Gpu can use its speed for this.
If you need to turn off GI for the GPU renderer, you can reduce the number GI bounces in the RT settings to 0. However, the GPU renderer relies on the GI to capture some components of the direct illumination as well (especially with large area lights), so if you set the GI bounces to 0 you may get different results from the production renderer.