In the bus also the FD's engage automatically. It is supposed to reduce workload, and it does.
But independence is another aspect.
One small trick that I do when I fly manually even with FD's, is to fly the pitch that I want, without over correcting for FD's. If FD's happen to match my pitch, that's fine. If not, I will not chase them unless, there is a big difference.
You can choose to have the FD's chasing your inputs by expecting the next required pitch.
Chuck Norris never follows his FD's. FD's follow chuck Norris.