It does look like you did get the top damage, torvos if on top of scoreboard and listed as top damage in chat
Edit: the one war crest after sc report in chat is the one for top damage.
as you can see torvos already got his crest for highest dmg then you killed him.
that means that by the time the SC ended falkvald did more dmg than you but the dmg counter continued resulting in a higher number on your screenshot, it is even possible to run around and kill ppl after the SC ended.