Can someone give me a quick rundown of what that first transaction achieves? Why is your account more secure afterwards?
This has relevance for cold storage, since it's not possible to send NXT into a verified account that has been created solely offline. Although you can create the address easily enough and send funds to it, what's the trade-off with connecting it to the web for that one transaction and the security it brings?
I can't explain from the level of the code (I don't think that is what you want anyway

) but...
An account without an outgoing transaction has 64 bit encryption. When you send an outgoing transaction, the account number (public key) is registered on the Nxt Blockchain. This then provides the account with 265 bit encryption.
As I understand it, it is possible that 64 bit could be bruteforced within 2-3 years. 256 bit makes it practically impossible to bruteforce.