yes it's normal, how it should be.
In yor case you can select "cancel" because you faces do not need to be trimmed.
But in this case you should select done, than select faces that you wont to delete. It's like usual trim function work nothing new)



Start your cube from rectangle and then extrude it than try repair it and you will see what I'm talking about.
This cube is very simple examples, when working appears very complex solids and this method works well.