I realized what I was doing wrong (or incomplete).
The jacoco-it.exec file that was generated had all the information, but it was not being published to target/site/index.html file for external classes, which was being generated in 'report-integration' goal.

I had to run a separate command using jacococli.jar on the generated .exec file and specify my classfiles and sourcefiles. That gave me the coverage that I was looking for.