Does SAP want to know what their customers do?
My colleague is working hard for many months already to clean such old inconsistent data, alone for purchase orders we have more than 20 different issues identified, that need individual treatment, usually ABAPs manipulating table entries (but that is nothing really different to the reports from your mentioned notes, they also do table updates). Good thing is that this data is older than 10 years and not anymore audit relevant.
If you migrate systems then it is probably very easy to define some migration rules which prevent that such items get carried over to the target system.