To be honest .. I never looked into that feature ..
But I assume it has to do with the "override_transfer" operation that is not implemented in the GUI yet ..
That stinks. I was looking to setup a UIA as a gateway between an alt currency and bitshares exchange. Basically, user transfers alt currency to me, then I transfer UIA to them in bitshares. The do the reverse to cash out alt currency. That all hinges on the transfer of the asset. Would asset owners need to use the CLI wallet to make the transfer then?
I could setup a smart coin, but I don't have much BTS to fill the initial collateral pool. In addition, I don't quite understand how the smartcoin owner could then withdraw it from the bitshares exchange, if they can at all.