In my experience, both Pat Hendricks and Ulf Evenås uses henka waza in a similar manner to Corallini, a change in how a technique is performed, not a change to a different technique. Ie nikkyo henka is still nikkyo, just a version that is not the basic one.
That is also how I learned to use the term Henka Waza.
The problem is that I don't know if a definition update is needed for the Henka Waza definition in the AikiWiki. Maybe just some additional definitions. I think getting a "definitive" definition might be impossible.