Float values with the meta tag expose on spawn aren't retaining their value when the value is set with a Spawn Actor node. It appears to only be floats. Maybe it has something to do with the change to Float Real in Blueprints.
If you make a Blueprint of the c++ class you get the same results. Setting the value in code, or in the blueprint works as expected.
5.0 is printed out
0.0 is printed out
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-143935 in the post.