Direct Routing channel outputs are post fade and panner.
They have no independent level controls as do sends.
They are either on or off.
I believe their main function is to allow one to produce stems - which when doing post work are submixes of related material - like sound effects, Nats, Strings, percussion, etc.
With these direct outs you can export your main mix AND several “stems” all in one go.
These “stems” allow for more flexibility in the final mix to picture - and also allow for easier last minute editing.
However, the direct outs are what they are. They can send a channel to groups, also (always post fade). Their on/off state can, of course, be automated. I’m sure there are other creative possibilities here.
Hugh