You’re confusing two concepts. The fact that the SOAP adapter supports two-way operations doesn’t change the relationship between ports, adapters and handlers.
What I mean by this is that for a send port, even a two-way one, what matters is still the send handler associated with the adapter. The receive handler doesn’t enter the equation at all.
Similarly, if you’re talking about a receive location, the fact that the port might be two way doesn’t change that only the receive handler is important there.
The thing with isolated hosts and isolated handlers is related to the fact that the *receive* side of the SOAP adapter (i.e. receive locations, NOT receiving responses in send ports) runs in IIS, and thus must run in the context of an isolated host.
Does this clear things up a bit?