CreateAction with mountUsing() to set specific Field - Default Values are not applied (?!)

Hi! I am trying to fill a form's field with the Reference of an ownerRecord() of RelationManager or a Page that Manages Related Records. For that I have a CreateAction that uses mountUsing() to fill the specific select with the id of the Owning Reccord. This works, BUT: overwriting the internal mount with "mountUsing" results in a form where all default values are null and I use the Form from a Resource that has a lot of default values applied to it. Follow up Question: is it possible, to programmatically call callAfterStateUpdated() for a field? I have some extensive sync between fields via $set/$get, so my strategy was to set the related ID and then manually triggering a change Event, so that all the updates are done by the form. Thanks!