If you comment out line 23:
b2.position = ...
You will see that it looks alright before updating the child bone’s position.
Here’s another example
In line mode the parent bone points to the child bone as I would expect.
UPDATE
…you have multiple congruent posts about this so at this point Im not sure which to address and which overlap.
Well, this thread is about the SkeletonViewer.
The other is about how to freeze transformations of a bone / rest pose problems.
There is a third thread about not being able to transfer animations to an imported skeleton (which I gave up on).