but he is not sending bitcoin! he is sending the private key. it is like giving someone key to your home and to the safe in the wall so that they can go there and take the money you left them there. well that is not sending bitcoin.
additionally he is using shortwave radio so i wouldn't call that exactly "offline", that is just another digital form of transferring data. not to mention this whole thing is super risky since it can be intercepted in the middle.
+1
Very well explained.
The transaction was anyway broadcasted on the blockchain by the receiver. Eventually a person does need to have an internet connection if he wants to broadcast his transaction on the blockchain.
Second thing is that brainwallets are riskier and should be avoided since a slight memory loss could result in loosing your bitcoins forever.