And really the main thing that I think it would be mostly used for is actually boolean union, not so much for boolean difference. More for stuff like this where you've got a thin walled object:




And then you want to union on some other piece such as this:




But you don't want to include the piece of the handle that's sticking into the inside of the bowl, you only wanted the part going to the outside. Previously to get that you'd need to do some extra prep work steps on the handle to carve off some of it before you would be ready to do a union of it. With the new face subset booleans you can select the handle and then select just the outer face of the bowl and get this result with just one Union operation:




So anyway that's the primary use case. I figured might as well make it work with boolean difference as well because it could be convenient with similar thin walled objects to only cut some spots and not others. But still a cut with a curve is meant to cut all the way through those pieces.

- Michael