And Minaret Summit Rd. was then identified as a national monument road. Only later, after usanp activation, did we realize that it was only a Forest Service road connecting a national monument to a state route.
Very true - this "who maintains it" issue is different to the "this is not a sufficiently major road" and "should only include significant routes" objections that I was addressing.
Personally, while the USFS is a different department of the Federal Government to the NPS, it's not dissimilar to cities maintaining parts of US/state routes (eg those places in Colorado where the State DOT handed the route to a city and wrote to AASHTO to delete the route from the official route logs within the city limits, but the route remained signed and so we decided to not create a mile and a half gap just because the maintainer changed). And it engages with an NPS unit, though it not entering makes it a little fudgy and, IMV, maintainers choice whether it should stay or go.
The Mormon Emigrant Trail, however, is more fudgy - it's clearly in a National Forest, rather than a National Park, Parkway, Monument or Recreational Area*. That said it is part of
an NPS National Historic Trail (or is it
this one - maps conflict with the
GIS having it as California NHT and the Pony Express NHT going along the parallel route to the north, but the
pdf map has it the other way round) - but these trails aren't so much continuous park units, but more like a way to designate a load of small sites along the way for preservation (and not necessarily by the NPS).
*Which, of course, can be Parks or Forest, but that's just more fudge rather than going all Vogony on it.