A crashing wave where the crest leads the trough would be like when you're surfing inside of a barrel wave. The crashing part is going over your head and landing in the trough.
In the case of this star simulation they are saying that the wave is crashing, but the crashing part is falling back on the back side of the wave instead of going forward over your head.
In the case of this star simulation they are saying that the wave is crashing, but the crashing part is falling back on the back side of the wave instead of going forward over your head.