Disabale Fields isn't working (Chaos Destruction)

hey devs , here i got 2 pictures :
1 is scene with “DisableField” for chaos Destruction
2 without “DisableField” for chaos Destruction

but as you can see there is no difference on performance , FPS even higher in 2nd case , so why is that ? Am i doing something wrong ? (i am using “FS_Disable_Plane” from Epics chaos example )