Why Does THerta´s Enhanced Skill Only Give 3 Instances Of Jade Stacks?

Been watching some showcases and noticed that when THerta casts her enhanced skill, Jade only gets 3 instances of stacks. This got me confused in regards of her enhanced E dealing 4 instances of damage. In multiple different showcases, the final aoe attack of her enhanced e didn´t give Jade any stacks at all.

Can someone tell me which mechanic i overlooked?