As for Bevab, I can't comment. I'm not sure if you can post if you have restrictions. But I believe his claim. Think about it, he was being suspcious of mafia, and he claims he was Flitwick for his defence. But what if someone else was Flitwick and exposed him? Seems too much of a risk of a claim to make.
Flitwick is technically a lesser known character in Harry potter.
I mean recall how much do you remember of flitwick throughout the story?
I cannot recall him ever playing a much major role.
It would be more safer to character claim him rather than other characters.