What is causing pathauto to generate unwanted text in these URLs? I have configured pathauto to generate URLs for content according to this pattern article/[node:author]/[current-page:title]-[node:nid]. article is a literal input, to reflect the content type description Site Article not token generated.

The content type description is Site Article

The node title is: this is a title

The author's name is: nodecreator

The node id is: 101

When I generate the URL alias using the pattern article/[nodecreator]/[current-page:title]-[node:nid], the resulting path 's article/nodecreator/edit-site-article-this-is-a-title-101. The last section on the URL shouldn't be prefixed by edit-site-article.

What could be the cause?
Pathauto creates the alias when a node is being added or edited, so, if you are using current-page:title it will include the title that Drupal generates for that page, eg, in your case, "Edit Site Article: This is a title", and not just the title of the node.  So I would look into using node:title instead so as to remove any of those potential prefixings.