I am assuming they are still selling fixed weeks at Riviera, but I don't know for sure. A DVC Guide could tell you.
Does a fixed week actually work every year for the races? I am not sure how a fixed week works. I look at something like the marathon weekend in Jan and the the particular weekend can vary. Marathon weekend is always the weekend before the Martin Luther King weekend , and the Martin Luther King holiday is always the third Monday in Jan. In 2018, Jan 1 was a Monday and the marathon weekend was Jan 4-7, but in 2019 Jan 1 was a Tuesday making the marathon weekend Jan 10-13. Can one buy a fixed week that always covers the marathon weekend? The same issue can arise for the Princess half marathon weekend which is always the weekend after Presidents' Day, which is the third Monday of Feb. Another varying holiday: can one buy a fixed week that always starts on Easter Sunday or the day before?
I could maybe help with this. We own a Run Disney fixed week at CCV for Wine and Dine weekend. We enjoy the RD events, and picked W&D for our fixed week because of the lower points cost compared to Princess weekend, and the overrun with Food and Wine.
For the first question, our guide informed us RD fixed weeks were not available with Riviera, presumably because so few were sold with CCV (but regular non-event guaranteed weeks are available with Riviera). So we went with CCV before it sold out.
For the second question, yes, the fixed week is guaranteed to cover the RD event as long as the event continues to take place. If it's ever cancelled, it becomes a normal guaranteed week contract.
Our fixed week is week 44. With a normal check-in date of Sunday, for 2020 this week is November 1 - 8. W&D weekend is November 5 - 8, so in reality this particular week is just fine as long as one is ok with checking out and leaving right after the half marathon.
However, one of the perks is you're allowed to "float" your week, for lack of a better word. We received a call from Member Services over the weekend since our 11 month window is approaching, asking what dates we would like. Originally we knew we didn't want to check out after the half marathon, so we were going to book Monday November 2 through Monday November 9. After thinking some more, we decided we wanted to check in and race first, then stay the week after, so we requested check-in on Thursday November 5 and check out Thursday November 12.
The week has not actually been booked yet, but my understanding is it will still cost the 10% points premium despite not being exactly week 44 - in this case, 118 points total. But we are also allowed to stay less than 7 days as well should we so choose, and all of the booking will be handled by Member Services.
To be honest, after understanding how the RD weeks work, and knowing the CCV studio issues, I don't know why more of these weeks didn't sell. There's no downside except for the extra points that were required to be purchased. You don't have to register for the race, and as long as you don't mind going around the same time every year, you don't have to worry about not getting your studio at a hard to book resort. And you're not even locked in to the same week, or week days. We are very happy with this contract and the flexibility it offers.