They are not outside the blockchain..
Its like taking your wallet.dat and emailing it to someone else.
They open it, and have access to the coins located on the blockchain as they were before.
The coins are on the blockchain, but they never move.
that would require you to already have the exact amount of coins you want to send in a wallet address
I'm sure it will be streamlined and simplified for the end users. My explanation was as generic as I could explain it based on my understanding of the dev's post.