The damage calc from the battle between Politoed and Sylveon is just not possible with what we have today. Possible explanations I see are:
1. Sylveon has a Multiscale clone ability. Just as with Clond Nine and Air Lock, there may be a new ability like Multiscale but with a different name since as someone said, Sylveon don't have scale.
2. Sylveon has a new ability that reduce damage from crits.
3. Crits is nerfed.
4. The system did not allow the player from Gamefreak to lose.
Sylveon has cute charm, and why would the system be rigged for one person to win?