I do not use harness, so I am not the right person to answer
PS: It looks to me like the plan is to use harness to make design look more simple by hiding signals into it - some people like it, I prefer to have everything visible and I do not like to add unnecessary objects into schematic which could bring possible mistakes. Harness may have also some other features (e.g. when you use hierarchical designs (?)), but I have never really needed it.
PSS: I also prefer ports as I can automatically add page number where signal continues - I am not sure if that feature is available for harness