It's important to note the careful hedging in that response. Specifically:

* Activity Streams will be read-only, except through their (non-ostatus) API.

* No subscribing through pubsubhubbub "initially." It implies but does not promise eventually subscribing.

* Similar to streams, webfinger will be published but not consumed.

* From context, the final clause about inbound and outbound syndication is through some non-ostatus mechanism.