Yes, as it is a "lock".
The Project Access is controlled only on Montly validation.

for example a resource that works on 2 projects each project manager has the right to validate only the imputations of his project. Why does a project manager have the right to validate all resource imputations for both projects?

In fact it locks the whole week.
Any manager of both projects can lock / unlock the week.
The real "validation" is on monthly basis, on Project Consolidation.

I am talking about this, please why the project manager can validate all imputation of these resources
I would like the Project Manager to validate only the resource tasks in their project.

Yes, as of today, whatever the way you use, Weekly validation is global for the resource.

how i can increase the display restriction with the possibility to show only some of the validation request?  

You cannot do more than what is actually proposed.

i have already wokred with projeQtor and the access to list of project it 's limited, a project manager can't see all the project and validate the imputations