FWIW, @tylerboodman, what I’m talking about there is making the client-side Actions plugin API like the server-side Actions plugin API (which can return values while client-side Actions cannot, at present).
However, it’s true that the Return Data from API backend workflow action is only for one’s app’s exposed API endpoints. And you can, in fact, get the behavior of returning data from the backend in this way, if you set up an API connection to your own app’s API. (I know this seems weird and non-intuitive, but one can in fact do this. I’ve talked about this before in older videos and touch on it in this more recent video).