Been trying the new terrain hole feature. It doesn’t seem to use the center of the brush. Additionally I don’t think that showing the brushes palette at all is useful. And there is either a hole or not, opacity is irrelevant from what I understand.
By the way, should we post things about the holes here or in the 2019.3a forum?
Also, thanks for the feature 
It’s quite impressive. This sphere still bounces off the terrain, if I move the sphere a tad to the right, it falls through
Opacity does work but since it’s basically a clip operation and the surface mask texels are either 0 or 1 (to clip or not to clip) it feels different from the rest of the paint tools. If you change opacity you and paint, you’ll see that the threshold of the applied brush mask is actually modified.
The surface mask also uses the same texture dimensions as the control texture iirc which is why it doesn’t necessarily match up with the brush mask. That’s just a product of converting from world space brush to the terrains texel space
I also think the clipping it done based on the center of the texel meaning the brush opacity needs to be high enough to mask when sampled from uv + .5 * _TexelSize.zw
I think it would feel better if more central under the circle. Don’t want to make a mountain out of a holehill.