Last week, a KH6 uploaded our QSO with his correct grid (in KH6) but wrong DXCC country (US mainland), specifying neither CQ nor ITU zone.
LoTW evidently spotted the discrepancy, marking his grid [INVALID] and confirming the claimed country, unfortunately (right decision, wrong country). It didn't attempt to guess either zone.
At my suggestion, the Hawaiian ham kindly requested a replacement certificate with the correct DXCC country, then signed and uploaded the QSO again. This time, it was a perfect match. LoTW even correctly inferred both his zones.
I was pleasantly surprised to find that the original QSO match seems to have disappeared. I thought it might remain forever as a zombie. I guess if I (or anyone else?) had claimed the original confirmation for US mainland, the change would have caused headaches for the CPU but that's an edge case.