...Because if I had, I would have found out that several other people have tested the 'crochet takes more yarn' myth, some years before I thought about it. Oye. And the first one even referenced the same Yarn Harlot quote as me (and she has a page number, if you need it).
Sorry to say, I found all this as I was finishing the last swatch. Now, I just have to take pictures and do the measurements for what I have. One good thing, though...given the results above, I may do a garter stitch swatch in both needles sizes as well, as it seems that other testers have found single crochet and garter to be similar, instead of my assumption that stockinette would be the similar stitch. On the other hand, I then should do two double crochet swatches for the hell of it. That should cover all the basic stitches in both crafts.
So I may do four more swatches before posting my results. Or I may tally up my results for what I have, post that, formalize the rest of the test, and then do another post when I have all the results. We'll see.
I guess I shouldn't feel too bad. Testing things is all about the repetition from other people, in order to counteract your own test flaws and biases. So, let's see if I get the same results!