Non-Discretionary portfolios in GIPS

Why can’t non-discretionary portfolios can’t be added in a composite?

Because they don’t measure the manager’s skill; he (or she) is only a puppet.

You got a double negative there… if you’re asking why non-discretionary portfolios cant be in a composite, its because the manager doesnt have discretion… if they dont have discretion, it’s not their portfolio… It’s just them following instructions of the client.