I wasn't exactly advocating for it in a general sense. Someone mentioned the knot, and it was in my mind when I needed a knot, so I tied it, or as it turned out, by accident this other thing. It happened that I tied it with very different size and stiffness ropes too.
Anyway, yes, that's right, the one simple side merely makes a 270 helix. IN a stiff thick rope this helix gets laid into a 3/4 turn like a blackwall hitch (which is more complex than the simple side of a sheet bend*)with crossing point which is grabbed by something like a transom hitch(even if slightly incomplete/propped-up) formed of the thin soft rope (this can fold into something a bit different looking under load, and for that matter ends up gaining a u-turn). In identical ropes, (other than very stiff ones maybe? or possibly if dressed carefully -- How well does a sheet bend work if you dress the u-shaped rope as a straight line?), it works pretty poorly I'd think. So no, it doesn't stand up as an in-line loop. Since for bends you usually get access to at least one end, there are probably better bends one could tie too, but this seems to beat a simple sheet bend, certainly for slack security. (Recently I needed to tie a "midline bend" between a thick and thin rope, with access only to the end of the thick rope and while maintaining some light directional tension on the thin rope. Turns one's tying methods on end a little.)
I only thought it should also be a good loop when I thought it was a span loop. I didn't tie this during some knotting meditation, I tied it during real(non-critical obviously) use and just noticed what I had a chance to notice at the time, which still seems true other than the noted correction.
If you really care much, you have to try it. The horizontal overhand loop in the second picture is made with the thin rope, with its tail hanging down as the outgoing leg of the downward hangning loop. The upward going bight is made with the thick rope, and the two tails then get tucked up. Giver or take 180 degree twist of the tails, there are three dressings. I don't promise you'll be amazed, but it worked for me.