OK, that's kind of a technicality. I mean, he doesn't speak per se, but he has dialogue with thousands of people in the game. Come on!

he is a silent protagonist because he does not verbalize his thoughts.
compare it to Mass Effect. Shepard speaks what you tell him to

Yes, but isnt it implied that he says the words you picked? how else would the other characters how what he was saying?

Does this mean all those old games that didn't have voice acting count as a silent protagonist?

...no

The dude from GTA III was a good example of a silent protagonist, because he had no written or verbal dialogue.

Well in Mass Effect Shepard didn't always speak what you chose. He would say something along those lines. I guess Revan and the Exlie are considered to be Silent protagonists.

I dont want to argue this any further because I fear it will become a debate like the Unreliable Narrator one. All Im saying is that because they have lines of dialogue that you choose for them to say they are not silent protagonists, however I wont try to remove them because if people want them as silent prots they can stay that way.

He is not a silent protagonist.

Depends on your interpretation of the concept. As the article says:

A grayer territory is when the player is given a list of options when being spoken to, but never actually says anything either. For instance most BioWare games (Knights of the Old Republic, Jade Empire) require the player to navigate through dialogue trees when having a conversation, but the character never explicitly speaks, rather the player chooses and option, and the characters in the story react.