Is that really optimal? It is already true in that case that your colour schemes do not work for people with opinionated colour settings. Isn't this just relying on a quirk? The point of not using truecolor is to respect the colour preferences of the user.
Semantic styles limit the use - not all interfaces need e.g. "error" context. Take, for example, Task Warrior interface. There is no place for the "error" semantics in it. But there's a place for "critical task" semantics, which is usually also some shade of red.
