There is a huge difference between 2 days of rest and 4 days of rest. Real Betis has a huge advantage in this regard, 2 days of rest is unfortunately too little for Chelsea, they will come into the match a little tired. Let's see what kind of match we will watch tomorrow, Chelsea is the favorite but it is difficult to make a definite prediction since it is the final match.
First the game isn’t tomorrow if tomorrow happens to be 27th on according to your time but rather the game is Wednesday 28. Personally I agree with you on the take of Chelsea not getting enough rest I think the English premier league have been very nonchalant about teams in their league. In the past the last games of the season are usually played together same time but this season most leagues decided to twist the rules to accommodate their clubs playing European finals. Inter had same favour, Real Betis enjoyed same favour.
I was think that even if the premier league couldn’t detach the game of Chelsea due to how it will affect he table they could have simply shifted the whole final games to Saturday considering Manchester United and Tottenham had their finals played on Wednesday. This to me is part of the reason why English clubs hardly play well in European competitions, the fixture congestion is there eating up the players to fatigue