This is true, to a point. Link still has conversations with people, as we see in the games, but we never hear his voice, even in cutscenes. This is because Link is under the same pressure Zelda is in BOTW (Spoiler alert!) In BOTW, Zelda despises Link from the beginning because he mastered his gifts so easily. He ends up saving her life, and they slowly get closer. You find out that he rarely talks because he is under the same, if not more, pressure Zelda is, and needs to maintain as a figure of hope, so he stays mysterious, allowing the others living in Hyrule to stay strong with him.