A couple of things actually still care about this:
- The code that detects if we're running arc on arc, and then runs the arc we're running on instead of the arc we ran, checks for the project being "arcanist" (reenter_if_this_is_arcanist_or_libphutil()).
- Some of the symbol stuff still relies on it.
- Removing it was really more to prove it works (which it seems to) than to accomplish any concrete goals.