Wouldn't really be a retcon since we know almost nothing about his personal life. So not so much a retcon. Just giving more information
. Zemo we atleast saw some of his life and it appeared he was a humble family man who fought his way through the Sakovian military to become and elite black ops dude. That feels like a retcon, Mordo wouldn't have that issue I don't think. Though I don't need him to be a Baron. I like this version of Mordo and his motivations.