The actor played title character Jason Bourne in the first three movies of the action spy series, before bowing out and making way for Jeremy Renner to take over as new lead Aaron Cross in 2012's The Bourne Legacy.
Its sequel was due to hit cinemas in 2015, but producers at Universal Pictures have announced the film has since been pushed back to the summer of 2016.
Some reports suggested the move was to make way for the new N.W.A. biopic, Straight Outta Compton, while others speculated the date change was made to fit filming in with Damon's schedule, allowing his character to return to the big screen.
However, Marshall has since shot down the claims, revealing director Justin Lin's script simply wasn't ready to go into production.
He tells The Hollywood Reporter, "It's simply not true.
"Justin Lin is working with Andrew Baldwin on an Aaron Cross script/story that they pitched us a few months ago. I talk to Justin all the time and the script is not ready. It's a summer movie, and if we don't start preproduction now, we can't make next summer. Therefore, it's a wise decision to move to 2016."
Damon had previously insisted he would be open to reprising his Bourne role if Paul Greengrass, who directed him in 2004's The Bourne Supremacy and The Bourne Ultimatum in 2007, signed on as filmmaker.