I don't know anything about RestorePrivacy, so maybe they are paid to promote competing VPNs, or maybe they're not. 
Clearly the article has an anti-Windscribe slant based off the author's opinion of the company and its product, but if they don't trust article they can go read Windscribe's own blog post on the matter instead, which lays out the exact same information.
Any third-party uninstaller that deletes leftover program files should do.
