So is there like a delay in Malzahar's R suppression or what? It always happens later than it should

I always thought it was kind of like an instant ability, but the more I play with Malzahar, the more I realize how often I got disrupted trying to use it.

For instance, once when a Riven was going up against me, I used my R just as she was using her shield-dash into me and she hasn't even used her stun yet. But for some reason her stun's animation still went off, I got stunned, and my R went on cooldown.

Similar cases happens with all other CC's that could disrupt me. Other times when I try to use my R when my opponent is still atop my W, I always find that the opponent managed to just barely leave the zone of my W before my R could stop them in place.

Is there like an unmentioned delay before the suppression takes place or something?

If so.................why didn't the Champion Spotlight or Tooltip mention that?!?!?