There some subtle differences.

1. Unlike to LOAD_NAME, STORE_ANNOTATION doesn't fall back to globals if '__annotations__' is not found in locals. The behavior difference is shown by the following example:

    x: int
    class A:                                                                                                                                                                                                                    
        del __annotations__                                                                                                                                                                                                                    
        y: int

2. The single STORE_ANNOTATION is faster than 3 other opcodes.

3. It doesn't add a name constant. Instead it uses a name from the names list (which already has to contain this name).