The fact the Blackbeard grabbed Hancock and Coby hadn't moved implies he wasn't going to avoid it. If Oda wanted to show us Coby could avoid that kick he would have but he didn't he had someone stop her.
You can perceive an attack but still not be quick enough to do anything about it.
You can perceive an attack but still not be quick enough to do anything about it.
Infact I can argue him not moving means he was going to clash with it or tank it completely with tekkai infused with armament haki