Week 52 is definitely not an event week because when I bought my plat WMH in the Spring, that week was available (it was the only platinum week available since I bought sometime in April or May). However, it was booked quickly because sometime in July I tried to get a second unit for the same dates and there was no availability. My deed says 51 and 52 are floating for platinum.
I think if you own there you will be fine getting that week each year. Just book it before the 8 month window. If you don't own there, it is very variable. Perhaps right at the 8 month window.
I also tried to get Thanksgiving week with SOs this year and it was sold out at the 8 month mark! Bummer because it is a great time to visit the desert. Since it's Gold time, not Platinum, I could not book it at the 12 month mark.
Katherine