plenty of videos from nasa themselves showing how they "create" the CGI blue marble photos. no different process, and videos are easy to find.
Plenty?
Please show which "Blue Marbles" were made by combining high resolution data from low earth orbit satellites.
Even those were made from data from satellites, so I don't see what it does for your case.
And why is this an issue if NASA themselves publish the information
Data Visualizer and Designer Robert Simmon never thought that he would become “Mr. Blue Marble.” (https://www.nasa.gov/centers/goddard/about/people/RSimmon.html)
On reason for doing it that way is that a photo can only show a little less than one hemisphere but modern "blue marbles" can show many "layers" of the whole Globe.
Though the Russian satellite's 121-megapixel image of Earth is most detailed yet - the Verge. (https://www.theverge.com/2012/5/12/3016254/russian-satellite-earth-from-space-121-megapixels)
And what about this one? Apollo 17: Blue Marble
(https://www.nasa.gov/sites/default/files/thumbnails/image/as17-148-22727_lrg.jpg)
One of the most widely known photographs of Earth, this image was taken by the crew of the final Apollo mission as the crew made its way to the Moon. Dubbed the “Blue Marble,” Earth is revealed as both a vast planet home to billions of creatures and a beautiful orb capable of fitting into the pocket of the universe.
Apollo 17: Blue Marble (https://www.nasa.gov/image-feature/apollo-17-blue-marble)
No CGI there - it was taken on a real film camera by a real person.