[GAMEPLAY] Casting spells in Soraka's silence

I've noticed on multiple occasions that if Soraka puts her silence pool under a champion in Zhonya's, the champion can cast a spell as soon as the Zhonya's stasis ends even though the silence is still there. I think if they stay in the pool then the silence is applied after a second, but if the champion has a dash like LeBlanc, she can just dash out of the silence.