PROBLEM TO VALIDATE IF A USER HAS A PERMISSION

I do the validation as follows:

oEnlaceSBO = oCompañia.GetBusinessObject(BoObjectTypes.BoBridge)
oRecord = oEnlaceSBO.GetSystemPermission(oCompañia.UserName, sIdentificadorPermiso)

But although the user does not have permission the sentence always tells me that it has full authorization, but that is not true.

I think it is a bug of sap because using service layer happens the same, solve it by validating the permission through the tables OUSR and USR3.

I would like to know if this really is an SAP bug.