Thanks for sharing your viewpoint.
Some people are narrow gauge fans, some are standard gauge fans. I am a D&RGW fan. Some only care about what happened on the C&TS or D&S part of the D&RGW, There was a lot more to the D&RGW than just those two small portions. For exmaple, narrow gauge operations continued in the Leadville area until 1925, yet are totally unknown to most.
The railroad was a system and there was overlap between ops on the ng and standard gauge. For example, the D&RG used both narrow gauge and standard gauge rotary snow plows in Leadville. At least once, they put a standard gauge rotary (071) on narrow gauge trucks.
Doing two books would require an artificial separation of the two gauges that I do not think would make a logical story.