Currently the scorched duct, set to export byproducts (last option), does collect the slag byproduct, but it doesn't push the contents out to a chest that is next to it. I haven't tried force-pulling it out with any kind of item transfer tools.

utilizing ender IO item conduits do pull properly

I will state however, that without some form of pulling, when the duct gets full, it still doesn't push to the chest next to the duct, and will instead eject it in the world.

I think the feature was going to be rewritten and was removed in the meantime; will do during the next update