Another great example of how animators translate a story sketch into the staging for their scene.
This beautiful story sketch is of course by Bill Peet, who's drawings always stimulated the animators' imagination. There are whole sequences in 101 Dalmatians and The Sword in the Stone that maintained Peet's story continuity and staging. Virtually no changes from story sketch to final film frame.
In this scene Merlin is pouring some tea for Wart who just "dropped in". Ollie loosened up Wart's pose a little. Holding his arms behind his back probably didn't feel natural to him.
As the table grew larger in the final layout there was a chance for Merlin to lean forward into a different pose. All this is called plussing.
You evaluate what a story artist and a layout man came up with, and you add your own vision to the scene.
This type of teamwork was essential to achieve top quality in Disney's classics. It was also essential for the films I worked on like Mermaid, Beauty & the Beast, The Lion King and all the others.