Why do invisible FoliageInstances still have collision?

I reduced the Foliage in the level using the foliage.DensityScale command. However, when I use this command, the hidden Foliage Instances become invisible but still detectable by LineTrace, returning Hit results. The collision component is UFoliageInstancedStaticMeshComponent. Is there a way for me to determine when a currently hit Foliage Instance has been hidden when using collision detection?