Hi Ricardo,
In my opinion making 0MATERIAL__0MATL_GROUP authorization relevant should not have an impact on performance. The authorization check will check the selection(s) in the query (i.e. the WHERE clause in the SELECT statement) against the authorization. If your selection fits within the authorization, then you can continue, otherwise it will issue "no authorization".
Maybe you setup a test case in a QA system or so. If you have here the same or representative master data, then you can measure performance prior to applying it in the Production environment.
Best regards,
Sander