This year it was still called 150 class but the class was extended to 159.9 max legal weight
From Japan open site:
Sanctioned as a "150-class" PDGA Major, players can thrown only discs that weigh-in at less than 159.9 grams. This is a legacy from where the event originated in the highly populated Tokyo city park courses three decades ago. This lighter class of discs requires a steep learning curve for our players under the best conditions, but can also be a huge liability with the winds that are known to course down the Nasu Highlands mountainside during this beginning of the annual rainy season in Japan.
Actually there are two classes now. 150 class is up to 151.9 grams and 150 open class is up to 159.9 grams. We can only play open class on a closed course. Any tournaments at public courses are still limited to 150 class.