If there is no documentation designating a 'by this date' deliniation, then the Ex date is the ONLY one that has legal standing.
One, the market should have ceased trading of the stock since any buys/sells after the fact would have been moot. But since there is no such documentation EXCEPT the Ex-date filing, then trading is legal and valid up until the end of the Ex-date.
And anyone who shorted shares and didnt cover by the Ex date is liable for ALL repurcussions due to the action. (Divy, R/S, F/S) etc...
In fact, if an MM sold one share to a shareholder that was of a shorted nature, and would become 100 shares post split... the shorting entity is now responsible for all 100 shares.