Though the superman/locust one seems to bend the back less, so maybe it is worth a try to see how that one feels.

Yes, one difference would be that in Sphinx, you're using your arms to push your spine into the curved shape.

Whereas with superman/locust, you're lifting into it, and you can't go any further than the strength of your back muscles can take you. So, it might be different. Or not.

But if it doesn't feel right, definitely don't do it! It's certainly easy to compress your lower back in unhelpful ways with backbends.