I also checked it yesterday and after the match against Real Madrid and I saw the same thing too, honestly in terms of how they both play their football I think PSG will dominate that day, but Chelsea are also this side that have improved lately and can also cause damage from to any team. Considering the fact that PSG will dominate the play of course the odds will be in Favour of them. But I still believe before Sunday PSG odd will increase and Chelsea odd might reduce to 4odd.
Despite the odds being very likely to change before the final, I also think Chelsea will have a tough time facing PSG with their current squad. PSG's players still look quite exceptional at pressing opponents and making them panic in possession, which could lead them to a superior outcome in the final. However, in a final, no opponent should be underestimated, as any team will undoubtedly play exceptionally well and give their all, making the match much more intense than in previous matches.