Well, it is and it isn’t. If I had tens of thousands available, I could just pay a professional company to do an HDR scan of course. But someday I might have a way to do it cheaper. The current scans are done by people who do it as a hobby basically (not myself) and those don’t have HDR setups.
Most scans I’ve seen aren’t clipped, assuming you mean highlights. Some don’t have the best color grading though. As for the darks … talking about typical theatrical prints, HDR would do one thing and that’s reduce the noise in the dark areas. However it would not necessarily reveal a lot more detail or anything. Especially after an H264 encode, the difference is probably negligible. I’ve done HDR experiments and the difference is visible, but it’s not necessarily a “day a night” scenario.
Generally theatrical prints tend to have rather strong contrast and flatten out in the darks and bright areas. Scan quality does matter to a degree, you might lose dark detail with an extremely bad camera, but the cameras used for these projects tend to have a signal to noise ratio of about 70 dB or around 12 stops of dynamic range, which is generally speaking good enough to have an enjoyable scan.
If you’re into having all the details in the highlights and dark areas down to the last pixel, you’re probably better off watching Blu Rays that were scanned from the original camera negative, as the information is still present in that. More so than in the theatrical print anyway.