I think the problem with articles like this is the (natural) tendency of lay authors to try to simplify complicated scientific theory in order to make it accesible to the masses. An earlier post noted that the Lagrangian points that are most likely to be inhabited by a third body (ie., a larger planet) are actually 60 degrees (not 120) in front of and behind the smaller body.
You can not have a 'larger' (more massive) body in the L4 or L5 points. If you did, than it would become the planet and the original planet would occupy the Lagrange point.
In fact, the cumulative mass at any of the Lagrange points can not be greater than a small fraction to the planet. You might get something the size of the earth into Jupiter's L4 or L5 but you couldn't get something the size of Saturn. The two masses would destroy each others orbit.
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)