I disagree, taking into mind the nature of his attack. If I understand what you're saying, of course. 

The thing about it is that as Brennus' attack completes, he's been parried by Florian. To take any further action, Brennus needs to now bring his left foot forward to re-balance himself, considering how far ahead his right foot is. At this point, Florian has control of his sword arm. This is what I mean by the attack being slow. 

And at this point, there's not a lot Brennus can do. 

Even if he does jerk his arm back or sideways while off balance, his position doesn't change. Florian at this point can stab him anywhere he chooses.