Their referenced Arctic DEM gives a 2m resolution however on accuracy notes 'Without ground control points absolute accuracy is approximately 4 meters in horizontal and vertical planes'.
This is much better than most global data (SRTM and ASTER both at 30m resolution)
However it is not as high resolution as many existing free models for individual parts of the globe. As an example here in Australia I can get free 1m resolution DEMs of cities with accuracy noted at "0.3m (95% Confidence Interval) vertical and 0.8m (95% Confidence Interval) horizontal".
Basically fixes the problems with SRTM, but you're still left with 30m resolution.
You can read more about ArcticDEM here: https://www.pgc.umn.edu/data/arcticdem/
Seems like EarthDEM is the same. So all the advantages and disadvantages that come with stereo photogrammetry. Very high resolution, but potential for inaccuracy and quite difficult to check. Probably they used SRTM or something similar to validate their models.
>IceSAT altimetry data points are used to improve the vertical accuracy of both the DEM strips and mosaic files. IceSAT data points are filtered to exclude points in areas of high relief and over hydrographic features. Additional filtering is applied to remove altimetry points collected outside the temporal window of the source imagery acquisition date.
An xyz translation is calculated for each strip and the offset is added to the metadata file. The individual DEM strips are not translated before distribution. Users can apply their own corrections to the strip if they do not agree with the one originally provided.
Where available, additional control information such as LiDAR or surveyed GPS points have been applied.
They've changed quite a bit it since I last used it for my CS senior project a few years ago, but figured out you can see DEM segments for download by clicking the icon with the popup name "Layer List" then click "3DEP Elevation - Index", then "DEM Product Index". You will need a GIS program like QGIS or ArcGIS to view and raw DEM data.
However, it clearly doesn't do well with water, lots of "fake" terrain going on where the ocean meets the land.