Their own graphs don't even back up their headline. In fact, they may actually contradict it.
The 18-34 year old black line looks relatively flat across time. However when the graph says "Prevalence of divorced people age 18-34," it implies throughout the whole general population whether they married or not. With that it mind, and with people less likely to be married between the ages of 18-34 over time, then that suggests that divorce is actually rising (slightly) amongst younger generations (Millennials).