Bayern Munich beating out Union Berlin wasn't really unexpected, of course they won that game, and they are looking strong as ever yet again, which is what we come to expect from Bayern Munich usually ,it wasn't the case last season but this season they look like they are better at league once again so this win was expected and good.
I agree that this season Bayern Munich looks for sure better and good as they did the last season.
That they have won against Union Berlin was really not a sursprise and unexpected as you have written.
But there are a few things that they have to work on specially in there defense , they have sometimes some troubles.
I have absolutely no complaints about Bayern Munich's performance against Berlin. They have a solid attack and defence, a clean sheet, and good game management with minimum effort. They played more calmly in this game. It's great to see them keep their clean sheet after three games. Hopefully, they can defend this much longer.
I know you're worried about their defense when they face a high-profile opponent in the UCL. But, they're slowly improving. Their consistency in the Bundesliga will help them to bounce back.
It's pretty interesting to see how well Bayern Munich is to face a great opponent at UCL. They seem well prepared to face a tight game, and the game against Benfica is gonna be a good test.