In the book “MCU: The Reign of Marvel Studios,” co-authors Joanna Robinson, Dave Gonzales, and Gavin Edwards shed light on the reasons behind Whedon breaking Jackson's rule.
Whedon insisted on a scene featuring Fury running onto the deck of the Helicarrier with a rocket launcher. Despite Jackson's initial displeasure, he eventually gave his approval.
The authors highlight that when Jackson found and read the mistake in the script, he turned to Whedon in frustration and remarked, “‘What's this say here? It says I run!’”
Despite Jackson labeling Whedon a “motherf****r” for his preferences not being met, he took it in stride after Whedon assured him that, “’You only run once.’”