PostLoad function is not called for blueprint components added through code.
In 4.12.5 (CL 3039270) code components do have PostLoad called if other components are not added through the editor
in 4.13.2 (CL 3172292) code components do not have PostLoad called in any circumstance.
In 4.12, opening Positive will trigger breakpoint but opening Negative does not. In 4.13 and 4.14, nether Positive nor Negative trigger breakpoint
PostLoad is called for all components regardless of the other components in a blueprint.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-38234 in the post.