The importer-specific page directs the visitor to run a Ruby script instead of using the CLI provided by the plugin.
For example, the documentation for importing a wordpress.com
site directs the visitor to run:
$ ruby -r rubygems -e 'require "jekyll-import";
JekyllImport::Importers::WordpressDotCom.run({
"source" => "wordpress.xml",
"no_fetch_images" => false,
"assets_folder" => "assets"
})'
instead of
jekyll import wordpressdotcom