UTF8StreamJsonParser creates a child context every time:

• it encounters a property
• if the property is collection-like a new context is born for every element in the collection.

TreeTraversingParser instead creates a child context every time a new object has been created.
The result is that, for collection-like properties, the current value of the current context is first set with the container object, then with the collection itself.

I attach a small test case with two tests in which I created a DeserializerModifier to try to append a parent to all children objects.
jackson-bug-test.zip
I tried with versions 2.9.5 and 2.8.10.