Fiora's Riposte doesn't deny Braum's Concussive Blows

I have found theres discussion about the same situation too, without legit prove.

I was in an ARAM as Fiora. Theres Braum on the other side. I several skirmishes, I attempted to Riposte Braum's 4th AA that would trigger Concussive Blows. For all result that Riposte doesn't deny Concussive Blows, like parry the stun and stun the opponent instead. What happened were Braum triggers Concussive Blows after Riposte by the 4th AA.

I do understand thats would likely because Riposte also denies the AA applied thus prevent the stun triggering. So this might be universal to those other champions with "block" capability, yet I have not test it.

However I can't agree with this if its intended. I can't understand why would the parry not considering the on hit effect, specifically Braum's Concussive Blows. If a spell hit Riposte, the spell effect would be checked, so should the AA. I believe Riposte does parry Nautilus's Staggering Blow as it should be, so I wonder if this Fiora vs Braum a bug or not.