Signage on the USBRS is in a much better state today than ten years ago. The system has had something of a renaissance, but this doesn’t necessarily translate into funding for improved infrastructure beyond signs.
I’ll admit to some bias here, because I started mapping in the Miami Valley in Ohio, which has some of the best-connected rail trails in the country. Ohio’s second-generation state bike route system, a central part of the USBRS, owes its existence to a cyclist who documented long-standing and emerging trails on his website, popularizing the idea of them as a connected system and proposing a numbering system that caught on. Park operators collaborated with volunteers to put up wayfinding signs, and eventually the state highway department got on board. Today, the USBRS and state bike route shields get bolted onto the side of the Miami Valley signs, if at all.
I think it would be great if we could get to the point where bike route relations are primarily useful for rendering shields or drawing lines on a route-centric map, but would not unduly influence routing. Then it would be no problem if some of these routes are designated by private entities or secondary public entities but still meet our verifiability standards – like the Miami Valley trail network.
For this to work, we need more of the members of these relations to have details about bike lanes, surface, and so on. Until we can gather all that information, something like the proposed cycleway:hierarchy scheme would let us broadly characterize segments of each route.
By analogy, we still haven’t comprehensively tagged roadways with surface, speed limit, and other fine-grained details that would be useful to automotive routers, but they can still fall back to functional highway classification to some extent.