Changing a component's collision setting in a class constructor will update new instances of the class/component with the collision change, but new instances of a child BP do not reflect the change.
This is not a hot reload issue as the behavior is the same when compiling with the editor closed.
C++ Class instance shows collision setting as Ignore while blueprint instance still shows collision setting as Overlap
Both C++ class and blueprint have the same collision setting after updating the code.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-39981 in the post.