It depends on the child and situation. Only a fool would say always and only a fool would say never.
Generally speaking, if the lock is an real issue, that means the child desires it (if not don’t have one and who cares).
Generally speaking, when a child desires privacy, and the parents are completely unwilling to allow any such thing, their relationship is not going to be a healthy one.
Generally speaking, unhealthy parent/child relationships are the root cause of things like OTD teens.