Documenting the logic of affectation to projets

In the on-line documentation, there is no mention of implicite cascading rights of resources to projects and sub-projects.
ex: res1 is affected to project P. If P1 is a sub project of P, res1 is automatically affected to project P1. Although, it does not appear anywhere in the affectation tables. This implicite rule could be described and woulb ease the use of the appli for new boarders .
Thx!

Thanks!