Right, I think the problem is NW.js 0.22 is actually the first version that started using symlinks, and Windows has no concept of these symlinks at all, so they are completely lost via any way you try to copy the files. That's new and very awkward, since I'm not sure there's anything C2 itself can do to work around it...
Still, I found a workaround: on the Mac itself, download NW.js directly from https://nwjs.io/downloads/. (You should be able to do this with any version for the OS X export.) Extract the NW.js download on the Mac. It should run because it has preserved the file permissions, since you did everything on the Mac. Then export with C2 and copy the files over to the Mac any way, it doesn't matter how any more. You can open the app folder by right-clicking and selecting "Show Package Contents". Using that, you can open the C2 exported app, and copy the Contents/Resources folder. Then open the NW.js download and delete the Contents/Resources folder, and paste in the one from C2.
That basically copies the C2 game data in to an ordinary NW.js download. It seems to make a working macOS app for me which runs the game OK. It's a bit of a bigger file since C2 strips out some stuff it doesn't need, like the pnacl stuff. You can delete it yourself by going to a path in the package like Contents/Versions/<version>/nwjs Framework.framework/Internet Plug-Ins and delete the contents of that folder (a .nexe file and pnacl). That should strip ~20mb or so.