I think the absence of a citation, is the answer to my question. My only question was whether I had overlooked a body of documentation. Don't think it was meant as criticism. I'm a Wolfram documentation booster. In general, it's a gateway, not a barrier. FinancialData properties is a rare case where variability of financial terms is greater than is the case with many other Mathematica functions that use centuries-old well-defined math jargon.

Thanks, Lewis. Thumbs up.

Your list is more helpful than the one in FinancialData[] documentation. But it still leaves a lot to experimentation and even further research in a few cases. I posted the question hoping Wolfram had a stash of details waiting for me to discover.

Take "CumulativeReturn" and "CumulativeFractionalChange". Both return a TimeSeries, which is nice, but it's not a number as the description suggested to me. Both return fractions. If my guess is right, the difference is that the former includes distributions, though I haven't done enough research to be sure. Even if I'm right, I'm not sure how to determine handling of reinvestment.

In some cases, description leaves details to imagination. Dividend says, "...can be trailing or forward."

I think the ambiguity of documentation I've seen so far is a barrier to the platform.