Dungeon World – Do I currently understand the shape transformation and custom moves as a druid?

Custom trains:

However, if I have to climb onto a tree (still in bear form) to avoid a danger on the ground, I now use a custom movement that offers me the bear form: Natural Born Climber. In my natural form this could be a Defy Danger role to build the tree … but bears do not have to try to make a tree, they just do it. In bear form I spend a stop and climb only on the tree (no litter required).

The actual custom movement would look like this:

Naturally born mountaineer – With your strong buttocks and razor-sharp claws, you can climb almost anything that "carries" your weight.

I understand that each animal's individual movements are subject to GM's approval. I'm just trying to take it from him by developing a series of "custom" custom moves for certain animals I rely on frequently (Fly, Swim, etc.).