Apple Motion 3 - Manual (Page 263)

Chapter 3 Basic Compositing 263
Rules for Transforming Selected Objects and Groups
The way you transform selected objects depends on how many objects are selected.
Transforming a Single Object
If you select a single object, the changes you make only affect that one object. All
unselected objects remain unaffected. For example, if you select a single object,
transform handles appear around that one object.
Transforming Multiple Objects
If you select multiple objects in the Canvas, changes made to one object are
simultaneously made to all others. Each transform occurs around each object’s own
anchor point, so the effect is the same as if you made the same transform to each
object’s handles, one object after another.
After scaling Before scaling
Before scaling After scaling