Chaining MetadataProvider and IdPv3

[Nate Klingenstein]

All,

Two quick questions:

https://wiki.shibboleth.net/confluence/display/IDP30/ChainingMetadataProvider
https://wiki.shibboleth.net/confluence/display/IDP30/MetadataConfiguration#MetadataConfiguration-SearchOrderingSearchOrdering

1)  Why was the Chaining MetadataProvider type brought forward to IdPv3?  Config compatibility, other?  Is it still mandatory?
2)  Is there any functional difference between having a Chaining element wrapped around two providers and having multiple EntityDescriptors beyond the modest control provided by the MetadataProvider configuration itself?

Thanks for your help,
Nate.