If you created linked child courses from the master course any changes should flow through. It should be easy enough to check. Make an activity in the master, then check the child course to see if it show up. The problem comes in when someone edits an activity in the child course. Say there is an assessment in the master course. If someone teaching from the child course decides they want to change a question or add/delete questions. That breaks the link with the master course (at least for that assessment). Any changes to that assessment in the master will no longer go to that child copy. It will, however go to other child copies assuming they haven't been altered.
At least that is my understanding based on how it was explained to me.
Was this addressed in a ticket with Agilix Support regarding course copies and nested course cards? Or is this something different? Do you mean the inheritance process of master and child course as Bruce stated, or content templates?