This isn't a way to stop piracy, it's a way to steal money from people who actually buy the games.
No...
It's saying "If you want DLC, buy the game. If you pirate it, it's your loss." They don't make you buy the DLC either, it's optional.
It mentions paying for that extra content. It sounds to me that they're thinking of taking parts out of the game and selling it via DLC.
This was one of the initial fears that people had with the idea of DLC, that game elements would be held back intentionally for DLC just to make more money. Personally, I don't think the majority of development studies do this.
They finish the game then while they're waiting on getting onto the next project and the game being published, they think of cool stuff that would be nice in the game.
Of course I could be completely wrong and everyone in the industry could be intentionally screwing over customers to make more money.
Currently, I don't think the majority of developers intentionally hold back content, but I know for a fact Capcom and Namco are guilty of this, leaving DLC bits on the actual disc. For example the versus mode DLC for RE5 only consists of an unlock code. Same with extra characters for Soulcalibur IV.
A lot of companies do this, especially on the PS3 where they can use Bluray discs which has a lot more storage. The content is already stored on the disc, purchasing DLC just unlocks the content from the disc. So I agree on the intentionally holding back comment (not that I'm saying all companies do this though). But with the storage capacity of Bluray, companies can fit a whole lot more data on the disc. So to make more money they just hold back on some of the content and release it as DLC (which is really just an unlock).
This isn't a way to stop piracy, it's a way to steal money from people who actually buy the games.