I was thinking why my first solution with the distance tool is not accurate and I found out that the distance tool is behaving strange.
As you can see in my screenshot the distance from the output to both of the points in the Input are not the same.
The Output is exactly the same point like produced with my other two solutions (create centroid in summarize tool and an arithmetic solution) so it has to be the distance tool that produces wrong numbers.
Can anyone explain that to me? Is it not the airline distance?