Yup, as I suspected ....
The feeders have their conduit connect to an open bracket. The wires exit the pipe and have crimp-on lugs that bolt directly to the bussbars. There are fiberboard separators between the bussbars at this point, so the lugs (and your wrench) can't strike another buss.
The crane bridge connects to the bussbars with spring-loaded copper shoes.
While the bussbars appear to be 'open,' it's actually somewhat difficult to actually touch them, either with your fingers or with a tool.
