I like these. See, to me this is what HDR is for. You recover some shadow detail without blowing the whites, or keep highlights without blackening the shadows.
These days someone says "HDR" and you expect something overdone to the point of looking cartoony, painted, or metallic. That might be OK as an "art form" but I don't care for it at all. (Opinion, of course.)
These, though, show what HDR is described as being able to do, bring extremes of dynamic range into a single frame. (Back in the days when I almost worked in audio, we called that "compression." Somehow in imaging we compress the dynamic range so it all shows up together and call it "high"......)
I was never lucky enough to see or photograph a rainbow at the Grand Canyon. Last time, at the North Rim, there was enough light at sunset and sunrise for decent video, nothing comparable to your still.
Your technique also solved the problem I had with Zion, difficulty framing any great shot from directly inside the National Park, peaks on every side.
This creative outside angle uses the Virgin River to highlight one of the mountains. If I ever get back to Zion, I will try to emulate your approach.