The new offsetSubD command seems reliable and I can’t seem to break it no matter what I feed it.
One possible bug: it seems like currently, the offset distance ends up being represented accurately in faceted display mode, across vertices from the original surface to the new one. This happens regardless of choosing solid output or not.
If possible, I think it would be better for the offset distance to be represented accurately in smooth mode. By this I mean that if you input a subD cylinder with one of it’s caps removed, and set a thickness of .250, the command should produce a subD cup that has a wall thickness of .250 in smooth mode, as measured by a line normal to the inner and outer surfaces. Obviously there would be some level of variation for more complex surfaces, but the target should be that distance in smooth mode, not faceted mode. Currently the output in smooth mode seems to be about 10% thinner than specified when I test it with simple objects.