Oversampling before private training puts each record and its synthetic copies in one correlated group, so a record-level guarantee silently becomes a group-level one.
Sensitivity, composition, and the accounting that has to hold end to end before a privacy budget means anything.
A review of eprint 2018/442 checked against both published revisions and the reference implementation, including a routing typo in the 4-party protocol that hands one server the plaintext.