For posterity's sake, if you insist on replying to me in two seperate threads, here is an excerpt from my reply there:

...probably moot if these "third party service providers" are just doing the busywork of interacting with the protocol, on behalf of Coinbase, on behalf of the user. I grant that this involves a kind of custody management you don't see in other non-securitized IT services, but as long as everything is spelled out clearly (which it seems to be in the excerpt you posted) I maintain my position.