Here's another reorientation situation with a Boolean operation.
Let's say I want to cut out a curve in the seat tube while keeping it's object orientation.
If you're using a Boolean Creator, orientation is taken from the Boolean Creator itself.
So I shift drag the Creator to the seat tube and then drag it out again without the shift key.
With the Boolean Modifier It comes from the first object in the hierarchy.
And with the Boolean Commands, it's about the one with the darker selection in the object browser.