Of course clicking the Telegram link can do some thing and that is it will redirect you to the channel or group although you can manually type in their name in the search box of the Telegram app and view the channel/group there. It's normal that we can see the contents even without joining them. That is the difference of a telegram channel from a group but it's going to be a hassle if you are going to check them from time to time if you won't click on the join button. Another perk of joining a channel/group is that you will have the option to receive notifications.

I think the main difference is that he has a full control of his channel than posting a thread here in the forum because it can get deleted by a moderator if they think it's inappropriate. Conversations inside telegram are also faster.