I just found out that the "Break Link and delete" option on relationships linked to full constituents does not really delete. Apparently BB has different definitions of delete.
If you choose the break link option then manually go delete the full constituent record the soft credits delete and there is no record lingering.
If you choose break link and delete - the record simply loses its ID but is still there in "ghost form" which still leaves the SCs.
So if you have a gift with these SCs and right click on the row in the SC tab which gives you the "go to FN LN" option you can open this "ghost record" once you have you can hit save which puts the record back in place linked still to the original record. LOVELY.
Even if you do not hit save this "ghost record" is now in your recently access records for you to open, edit, etc. even though it technically does not exist and can not be found in a search.
The KB solution was published just today because I brought this to their attention.
Please sign up to be noptified when this is fixed. although you can not be 'added to the list' any longer - maybe the more people on the notification list the more it is prioritized... maybe? Who knows anymore