The cov2sde command does not convert coverage pseudo-items (fields that begin with a "$") when loading coverages into ArcSDE layers.
This is not supported.
Solution or Workaround
There are at least two possible work-arounds.
ArcCatalog does see pseudo-items, so it can be used to load the coverage instead of cov2sde.
1. In ArcCatalog, right-click on the spatial database connection and navigate to Import > Coverage to Geodatabase.
2. Fill out the form, paying attention to the Item Names tab in Change Settings area; these items will be renamed. You may control the renaming if you wish.
In ArcInfo Workstation, you may create new items and calculate over the values from the pseudo-items that you wish to import. See ArcDocs for help on creating new items and calculating values from one item to another.