Possible bug: Sterak's didn't proc due to CC

In the clip, we can clearly see Jax has Sterak's proc is available. Jax gets CC'ed (airborne into stun), then the Sterak's passive looks as though it is disabled (it has a red 'X' through it).

Jax loses most of his health, then comes out of CC at about 10% HP. He dies, without Sterak's going off.

So what we can see from the clip, Sterak's not only does not activate while under hard CC, but the trigger damage does not accrue.