As nubbly stated picking up the show cage allows the opportunity to view the bird in a different light, particularly important for the ino varieties. It provides an opportunity to check body colour suffusion, eye colour and tail quill and flight colours eg cinnamon greywings it also provides different perspectives to the bird particularly useful in the top down view to gauge substance. Most judges will use this technique to some extent. i doubt that ring reading is an issue, if you ever judge at a budgie show your focus is elsewhere and apart from checking the ring colour in young bird classes you simply don't have time to read rings. The UK standard show cage size is within millimetres of the Australian cage, they, on average, just have bigger budgies and that is why the cage looks smaller.