REGRESSION: This regressed between 4.23 and 4.24
Assets set directly in a soft object reference pin on a blueprint function are not correctly referenced.
See UDN: https://udn.unrealengine.com/questions/563593/view.html
RESULT
You will see a reference to the RefByVariable material (which is referenced in a variable in the BP), but not to the DirectRef material (which is set directly in a node param).
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-90922 in the post.