The Javadoc for @InjectContainer could be more clear wrt. what is injected.
"Used in inject the container of a component as a field of the component. The container of a mixin is the component to which the mixin is attached."
It should be:
"Injects the component which contains this component, or null for the root component. For mixins, this injects the componet to which the mixin is attached."
Taken from ComponentResources#getContainer.