I don't see how a fully separated bike could be less safe.
But my definition of a fully separated bike path means it NEVER intersects a street. From what I have seen in the Southern California 'fully separated' bike paths that do intersect streets means dangerous intersections where bikes cross at a point where drivers do to expect anything.
An interesting point there. there is a bike path parallel o the Orange line. Officially the path ends and restarts with e street crossing. Thus all the street crossing accidents are officially not on the path.
On another thread I saw examples of Dutch paths and 'similar' U.S. paths and proposals. There was a significant difference. The Dutch paths are separate but close and very visible to drivers. U.S. paths just enough farther separated and often behind parked cars to be 'out of sight, out of mind'. That is until intersections where cyclists 'come out of nowhere'.