Well, if you hadn't been thinking about the fact that he only uses text, you would not have thought about why he prefers it. The fact he prefers text brought up why he does - that being his facade. So, focus on what brought that up. The text.

And it depends on the situation. In this case, it's a good thing. He prefers using text, meaning you are able to use text with him without it being questioned, giving you more chances to think first before you say anything.