I did not find a solution on my own, unfortunately.
Just tried your command and it works amazingly well in my scenes, even without object behind (just sky). Thanks a lot for sharing it!
Maybe it is because I optimized my hair a bit using the interpolation technique.
Here’s how:
Change Decimations values in your groom’s asset to reduce vertices. I used the following values
Then increase Hair Width to make hair look like before, but just a bit thicker, visually it will be hard to tell the difference, but it will speed up your renders by a lot.
Please let me know if it helps. And also, what background you’re using?