This enables an extra layer of control in the sculpt brushes.
For now it is enabled only in Scrape, but it should work in all brushes (like normal radius). I think we can safely enable this in 2.81 if we keep it this way.
You can tweak in this property in the scrape brush to achieve a much better behavior when working on curve surfaces and control how much volume you want to trim. In most cases, it also fixes the bug where the brush keeps trimming in the same area without disabling accumulate. I can probably fix some other artifacts in other brushes by tweaking this value.