Working in a part structure which is not CAD-driven I'm able to edit the positions of parts in Creo View and commit to Windchill using the command "Save Part Location".
A very handy command in many situations, how ever this commit will not create a new iteration in Windchill.
In some cases you add parts / resources to your structure with the intention to add positition in a later stage but if you use MPMLink to populate mbom, occurrencers are copied with position and then no manual change of position is expected.
Trying to change the position of a part in Windchill, parent is automatically checked out.
I expect a consistent behaviour where I'm able to follow up on who did what and be able to reverse unintended changes.