None of the pictures in Eaton's catalog show the jumper. It is shown as a Two-Pole—480 Vac—600 Vac or Vdc 1 (Suitable for Service Entrance Use with a Neutral Kit Installed). I wonder if there were instructions to add the jumper when you use it as a DC disconnect.
This came up in a discussion with an Eaton distributor a while back and I was told it was part of a "standardization" so they had one switch that could be used in more than one application (such as AC or DC).
Eaton's "line" was that there distributor would only need to stock 1 item to serve more than one requirement.