DVD has had a referral bonus program for at least the 5 years that I've been aware of DVC. So no, it's nothing new.
And it's not surprising that your Guide didn't mention it to you. After all, if they can get the sale without giving something to someone else, why not?
Keep in mind that some states do not allow the referral bonus due to their timeshare or real estate transaction laws. If you got the mailing, I'm thinking that your state is okay. But you can always check on that before submitting anyone's name.