Project Feeds are private and only viewable to Crew members of a given production.
You will see work from project/s you are on in your Activity Feed as it serves as a snapshot of all things happening for your in the community; i.e. projects you are on and people you are following.
However, do not post project work directly in the Activity Feed as it will be viewable to the entire community. Project work should be posted in the Project Feed directly.
Check out more details on how Feeds work in Artella here.