Romdane, Your Question is genuine, we can assign only one resource against a tasks/subtasks. But when we try this option from admin user , it will happen.

 
Try this case, Project Admin privileged employee A can assign a task to other employee B. Then Employee B will logon to the system and do a timesheet, you can see the difference. Under the employee dropdown, none of other employee never show except the logged employee.

Hello, Romdane!

Thank you for your question!

You are right. A task is to be assigned to one user, and you can have as many timesheets entries, by different employees, as you need (because, again, they work with employees).

I hope I could have helped, and that you are enjoying the lesson! :)

Cheers,

The Odoo eLearning Team.