I worked at a company which had a Unity builded codebase. The company had actually branched the codebase for two separate products. One of the products kept the .h/.cpp build running in CI in addition to the Unity build, the other product only used the Unity build.
My experience was that there was decent benefit to keeping the .h/.cpp build running. Most 'normal' C++ tools and IDEs are not going to assume you are using a Unity build and tend to choke on it. Even though we never really shipped anything from the non-Unity build, having it around was useful for avoiding 'phantom' errors in the IDE and having static analysis tools work properly.
My experience was that there was decent benefit to keeping the .h/.cpp build running. Most 'normal' C++ tools and IDEs are not going to assume you are using a Unity build and tend to choke on it. Even though we never really shipped anything from the non-Unity build, having it around was useful for avoiding 'phantom' errors in the IDE and having static analysis tools work properly.