Your question references ND filters which I think most would consider to be a solid ND filter. Those are mostly used to decrease your shutter speed for long exposures or by allowing you to open up your aperture for a more shallow depth of field in bright light.
A graduated ND filter is typically used to balance the exposure. With a traditional ND filter the top part of the filter is darker (by the rated stops for the filter) and it gradually moves to transparent. You place the darker part over the brightest parts of the scene (a bright sky) in order to properly expose the foreground.
In the foreground you do not lose shadow detail because it's viewed through the transparent part of the filter. If anything you gain shadow detail as you're able to properly expose it without the bright sky causing the foreground to underexpose.
However, if you have shadow detail you need preserved in the bright area...those would most likely be lost anyway due to the bright source and just about your only choice would be to use an HDR technique. Some of the highlights would be lost in the bright area but I think if you're trying to balance the overall exposure this is a point of choice - what do you want to show in the image? Before filters or HDR you always had to choose - expose for foreground or expose for the sky/background.
There are also reverse grad ND filters which help with sunsets/sunrises - when the brightest part of the sky is along the horizon line. You are able to preserve highlight and shadow detail in the sky above the sun due to how the graduation is applied to this filter. It's darkest at the center, bottom is transparent...but from the middle dark area it gradually lightens toward the top.