I've seen people throw around a popular headcanon that Link might be "selectively mute" (basically an anxiety disorder, often linked with select forms of autism, where a person who does have the ability to speak just very, very rarely ever does because of how anxiety inducing verbal communication is), and this image feels like a good example of that in action.

Fairly certain that's just Canon, considering what zelda's journal says in BOTW about why he doesn't speak.