Kevin Risden - Your concern is well founded. This however is a scenario related to KIP-8 where Ambari is the source for service discovery rather than the management platform that is pushing out all the config details. By allowing Knox to pull the relevant URLs and HA metadata from a service registry abstraction, we can have much simpler topology descriptors. Admins would only need to indicate which services they want in a topology and the rest will be pulled from the service registry. In this case, the Ambari REST APIs are used as the registry. Another source may be ZooKeeper.
So this is in a way simplifying what the Ambari UI needs to do - instead of all that XML we can have a simple page of services with checkboxes as well as allowing for the metadata to be pull from other sources if desired.
Give KIP-8 a read and see whether it makes sense to you.
Thank you for raising a concern here!