It appears that for spawnable bindings, when adding a child binding through a copy/paste it is not added to the child bindings array on the spawnable, so when GetChildPossessables is called, there are no bindings to add to the returned array. This impacts automated animation export workflows where child component bindings are often needed in the export as well.
Only one camera prints it's child bindings, even though both have child camera components. The child component that fails to print was added from a copy paste.
Actual repro for this after the fix is:
EXPECTED: There should be two CHILD BINDING : Camera Component printed to screen
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-121143 in the post.