From what I can see on that Tympanus example, once you click on it to show the options, the wrapper gets an added class.
The listitems have a transition delay. The first one has 0.05, the second 0.1, the third 0.15, etc. etc.
But when they’re wrapped in that added class, it’s the other way around: first one has 0.25, second one 0.2, third 0.15, etc.
So I guess the easiest way is just add a class to the outer wrapper once the item are visible.