I just faced the same issue. Was playing A.F.Kay, three of us left, thought it strange i had to play the same person twice, I beat them with the 3rd player also still alive but then was immediately given 2nd place.
In my case there was only me and another guy in the final, we fought twice in a row and i beat him twice. I was Curator he was Finley.
And after i won the second time hitting him for 32 while on he was on 7. i got a 2nbd place and no achievement for my win with Curator…