Why do some men seem introverted and quiet on the surface? But once you chat with him, he can keep typing and talking.

Can't say this is a man show. Everyone has different expressions. Some people are good at dealing with people and know how to get familiar with themselves. Some people don't want to talk to strangers and have different personalities, so they can't generalize. The boy you are talking about may be more emotional and sensitive, and it will be more natural to speak after getting familiar with each other. Another possibility is that he likes a person and speaks naturally. It's the same as seeing the person you like smile.