"Only the internal data table is shared". Does this mean the "Contents/Filled/filtered" data is shared?
Yes. The DefaultView of the data table is what makes the "fitler" happen. As for the contents and the filled data, yes as well.
"Any business object referencing this shared table is still a unique instance". Does this mean each instance of the BO has it's own data?
No. It means that if you call the navigate on one BO it will not affect any other BO using the same shared data table. This is when you will want to use a ChildFormDialog or a BOTranslation as the handlers and everything are translated between two or more sessions.
, will each one of these instances see the same record that was put in the mainform?
Any BO which has the same SharedDataTableKey will have the same data within the BO.