System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.28
Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-12-04 11:32, hash: rBf1aa4d18d49d
Short description of error
This may not be a bug and may be the intended result but regardless I still feel like the functionality is handled incorrectly. Personally I would assume the button would set the value to the stock HSV rather than just setting it to 0 , 0 , 0 (which is what it does). Anyone can go pure black, but it is much harder to replicate the stock value without copying it, resetting (everything) to default or looking it up online.
I have included a gif of how to recreate the issue.
Exact steps for others to reproduce the error
https://imgur.com/a/2HIoq6c