Let say we have this business unit hierarchy, where we set Manager BU to have the its parent = root BU. and we defined Region-A & Region-B to have their parent BU = Managers:-

and we granted Region-A business unit team read and write on all the records owned by region-A and same applies to region-B.. then will users inside the Managers business unit have automatically access to Region-A and Region-B records? or we need to explicitly set this?