Imagine what will happen if you manage a match with new version but switch to old version before the end the match.
There are many possibilities that new version may handle sp generated during matches for players with pending negotiation offers. I guess sp are created but are invisible in new version. These sp must be manually handled with old version unless new version will automatically use them after the negotiation offer is expired or rejected.
If you don't immediately reject nego offer, you may use old version to train players and play matches. But I don't recommend to train players alternatively with 2 different training systems. Some progresses may be lost.