You are probably right about the dates.. My WW did the exact same thing on our settlement agreement ( we weren’t married)..
The document stated 8th December 2018 as our split date. This was the day I ended it, after she refused to give up the OM.
2 months later she refused to sign the documents unless I changed the date to October. She insisted that we hadn’t slept in the same bed since October.. I gave up trying to convince her but refused to back down in the date.
I know she met / started to text and flirt with OM3 in November so can only assume she told him a load of lies ( I know she told him loads of lies about various other things ) about when we seperated.. hence I suspect she was worried if he ever saw the document it would make him wonder why..
It’s irrelevant now, but they always have their little motives.. I suspect self preservation to your ww is her priority..
Previous username - Helpme123.. A name chosen at a desperate time..
Now Mr Brightside.. coming out of my cage, and doing just fine.