I think the whole point is that Key is arguing the GCSB can only get metadata under a LI Warrant. That requires at least a shred of evidence to indicate that the individual is up to no good.
What I think Greenwald is saying is that isn't true and there is indiscriminate/wholesale gathering of metadata by the GCSB.
Let me state again.
The Internet is not secure.
Any one can gather the data and metadata.
Both Internet cables are already monitored by Five Eyes nations and any intel gained could be handed to the GCSB if the monitoring nation (US) deemed it appropriate.