A website has started several additional domains that are all keywords. They have then made one page websites for these keywords that are exact duplicates of the pages on their main site that they want to do well on those keywords. The links/navigation on the keyword name web sites all work normally, linking back to the main web site. When I research back-links for their main site, these keyword one page sites all show up as valuable back links. Does this method actually help? The master site DOES rank well for the keywords. I should note that some of these "keyword" sites have been up for a few years.