After contacting GitHub support about this, here is what they responded me with :
Just to clarify things, I did a bit more digging and found that if you
follow a user you will receive the following notifications:
- when they follow users
- when they star repositories
- when they fork or create a public repository
So it seems like you don't get notifications for every action they make. For that, you have to either:
- Check their public activity on their profile, or
- Watch a specific repo to get notifications for commits, etc.
While I understand that you would get tons of notifications if every action was displayed in the news feed, I'd like that we should at least have the control on which kind of notifications I want to see in my feed.