Hi,

Following upgrading to the latest version and using your new recommended search optimisation we have recieved this warning.

Is this something to be concerned about?

Search Console has identified that your site is affected by 1 Coverage issues: Top Warnings Warnings are suggestions for improvement. Some warnings can affect your appearance on Search; some might be reclassified as errors in the future. The following warnings were found on your site: Indexed, though blocked by robots.txt We recommend that you fix these issues when possible to enable the best experience and coverage in Google Search

It’s expected and usually nothing to worry about when content is deliberately blocked through a robots.txt. But have a look at the URLs it is giving as example and check to make sure that removing them from the index is okay. 

As @opentype mentioned, this is indeed expected behavior. However, review the URLs that are blocked to ensure that there are no base URLs in there.