For me, Safari scrolling is now very obviously 120hz. Make sure you don't have low power mode on.
You can also tell that Promotion is doing its thing because the frame rate ramps down in a bad way when the scrolling slows down. This behavior probably also exists in 60hz mode, but it was probably less obvious there due to the smaller drop.
Interestingly, testufo says Chrome is 120hz but says that Safari is still 60hz. Testufo also says that Safari is 30hz when low power mode is on, so I bet that Safari is still forcing some animations to stay at 60fps (for power usage?).