Landscape Grass Tool loss of Performance

A number of users are reporting a large drop in performance when working with the landscape grass tool compared to other foliage application methods, as well as a drop in performance since previous versions.

I have not been able to confirm the extreme differences in shadow performance on my machine, but there are enough users reporting this issue to merit an investigation. I was able to see slight differences in the shadow depth cost (images attached for comparison).

1. Open attached project.
2. In the default loaded level press PIE
3. Use the 'ProfileGPU' console command.
4. Observe results (specifically the cost of Shadow Depths)
5. Open the Painted Foliage map.
6. Repeat step 3 and observe the results.

Outcome The cost of shadow depths seems to be drastically different than the painted foliage map using the same landscape size/resolution/components.

Expected The shadow depths should be relatively close in cost when compared to other foliage tools.