Is this a bug or intentional

Ekko is able to cast his spells even after he was silenced.

The first time it happened was when I flash + Q as garen, he took the damage but was able to dash right afterwards. The second time was when I hit him with a rank 2 Q which is a 2 second silence duration, but he was able to take two steps before pressing R.

The whole premise of counterplaying Ekko is to CC him and kill him before he is able to R, but it seems he has a grace period before the CC or at least silence to take effect after taking damage and he can activate his spells in this timeframe. I don't know if he has the same grace period with stuns, charm, or displacement.