Meetings and tasks are not private
When you create meetings and tasks everyone registered to any project can see them.
There is no privacy at all in the calendars employees can see what meetings have the managers and what tasks are due to them, they see who is the owner of the task that is not correct.
Also in the dashboard of each project you have the meetings and tasks listed of every project so whats the point of registering users per project if they can see everything in the dashboard