Comment on WordPress SEO Google XML Sitemap by SEO Dave.
Although pages on this site are found for the test SERP “Free Unlimited XML Sitemap Generator Test”, it’s not the unlinked comment that’s ranking, it’s the main post.
Only when you do an exact Google search (within “speech marks”) does the unlinked test comment rank number one in Google.
This exact search with speech marks: “Free Unlimited XML Sitemap Generator Test”
Right now (May 31st 2014) there are 60+ results, all of them from this site (no other website uses that exact phrase).
Now compare to the standard Google search without the speech marks. Google lists just under 10,000 pages found (remember no site other than this one uses the exact phrase) and the first listing from this site is the main Google XML Sitemaps article (which is linked multiple times), not the unlinked comment. The main article is listed in Google at around 13th, which isn’t a great result and will be based on the body text within the content (these comments use the phrase multiple times).
This tells us Google is spidering and indexing the unlinked page (that’s an interesting SEO test result), but Google doesn’t appear to rank it particularly well for a standard Google search, I checked the top 100 results and didn’t find the unlinked comment: so it’s indexed, but not ranked for that SERP even though the title tag is an exact match (should be the best match from this domain).
As it is right now I don’t see much SEO value in having Google spider/index unlinked content via an XML sitemap, but then I don’t see any SEO harm in it either (I have the modified XML sitemap plugin running, so won’t disable it now).
The unlinked pages are unique content that isn’t costing me any PR/link benefit for Google to spider/index and long term other websites might link to these unlinked pages passing link benefit to the rest of the site. You also gain the tiny amount of intrinsic PR built into a web page for ‘free’, so overall might be helping the entire site SEO wise a very small amount.