Granting privileges on ALL_SA_USERS

I granted SELECT on the ALL_SA_USERS table to a role  and granted the role to a user.

Problem: When the user does a select on the ALL_SA_USERS table they are only able to view their own data even though they have been granted the role that has the select on ALL_SA_USERS. 

The user was also granted select on the DBA_SA_USERS table through a role and when the user selects from DBA_SA_USERS they are able to see all data in the table including their own.

Question: Why can the user see the data when using the DBA_SA_USERS table, but not when selecting from the ALL_SA_USERS table?