I maintain that Pierce's character assessment of Fury was not based on anything happening overnight, and by the first time we see him in the post credits scene of Iron Man in 2008--presumably that's real world time--he already has a cold, darker edge. By the time he became director of SHIELD--with all of what its known about the agency throughout its history, he had to have a larger, grim outlook on the world...on top of all of the non-otherworldly threats he faced over the years, requiring an uncompromising, violent response/mindset. When an "oddity" comes to earth, and he eventually believes Danvers to have an extraterrestrial association, his reactions should been more "on point" instead of behaving as if he was going along for the ride as a newcomer to everything.