Hey ,
I wanted to let you know that I reached out to our Developers and the behavior from these blueprints are expected. By default, the root component is selected to be moved (it’s the UpdatedComponent of the MovementComponent), which can have another component selected if desired. However, we only support collision for the component that is selected (attached components are teleported).
We plan to update the comment on MovementComponent, FloatingPawnMovement and RotatingMovementComponent in 4.9.
Normally the root component of the owning actor is moved, however another component may be selected (see SetUpdatedComponent()).
During swept (non-teleporting) movement, only collision of UpdatedComponent is considered, child components will be teleported to the end location.
Also, by selecting something other than the root component, you’d move that component and its children, not the root component (and therefore not the entire actor). It would be a relative change in location of the selected component.
I hope this information is useful to you and if you have any further questions, please let us know! Have a great day!