I want to point out something that has happened to me just a few times, and I'm sure some people will have this issue and some won't since it's totally based on how one designed their psd's.
When extracting something like this header here...
I get this result...
As you can see my designer just made a taller shape and moved it off canvas, something I wouldn't do but something my designer has done before, it's fine he doesn't think about that kind of thing a lot and I can just pull it into photoshop and cut the excess off, but I wanted to point this out and just put on the radar that this does happen sometimes and it would be awesome if parfait was smart enough to see the off canvas bit and cut it out of the asset extraction.
I agree with you - Parfait should crop the image and respect the document boundaries in this case. We're going to fix this - thanks for your report.