Loss of detail is due to clipping at either end (highlights or shadows) of one of more colour-channels. It's pretty easy to do in digital by cranking the saturation slider and there are plenty of people not paying attention in their postprocessing that will produce technically poor images. A saturation increase is a deliberate pushing of the channel values away from the grey line in colour-space and that will typically push values out of gamut especially near shadows and highlights. Values out of gamut means colour clipping, which means loss of detail.
RA4 absolutely can produce high saturation. I have a few wet prints here from Ektar and they are eye-bleedingly saturated, about on par with Velvia* though obviously the paper can represent much less total dynamic range. Yes, it has visibly more saturation than Provia. For example that image is a scan from the negative whereas the wet print is more contrasty (the tree reflections are close to black unless I dodge) and more saturated. There is no loss of detail anywhere in it.
It also helps that the only papers easily available in sheets are high-contrast, which increases saturation slightly. So even if you're printing with a lower-saturation film, the results are pretty strong-looking. Obviously though if you're shooting a high-contrast scene, you're going to struggle to get the whole image onto the paper without dodge+burn because the contrast is fixed (save for some rude tricks in developing the neg or print) and high.
* obviously it's the Kodak palette with strong reds instead of the Fujichrome palette with strong greens & purples.