class Bundler::GemVersionPromoter

def post_sort(result)

as not all elements are compared against each other.
Specific version moves can't always reliably be done during sorting 
def post_sort(result)
  # default :major behavior in Bundler does not do this
  return result if major?
  if unlocking_gem?
    result
  else
    move_version_to_end(result, @locked_version)
  end
end