Moscow has no jurisdiction and removing those items from an active crime scene is a violation of international law. Furthermore the black boxes will provide little, if any, helpful data. Any routing conversations would have been shared with ATC along the flight path and the moment of missile impact would have caused failure in aircraft systems monitoring.
But, again, let’s let the experts examine the boxes and not cart them off to a (SUPPOSEDLY (heavy sarcasm)) un-involved third-party nation.
Good you listened to that video...it’s “no longer existing”...been scrubbed.