Hmmm that's an interesting way to try and sell the fixed week option. It does guarantee entry for up to five people in the race, but I already own points at multiple other resorts. And with all the changes rD is making lately, no way I would add-on a fixed week for the term of DVC!
One thought... it does say it applies to marathon weekend, Princess, Dark Side and Wine & Dine, so I wonder if that's somewhat of a guarantee of those races being around for a certain amount of time? DVC is a decades-long commitment. Seems like they could be inviting trouble by using some races that will likely be much shorter lived to sell contracts.
ETA: I do notice it has the usual disclaimers at the bottom, saying this perk could go away at any time.