That would actually not surprise me at all. There are a lot of Web devs who can make a site that renders in the browser and mostly works, but can't wrap their minds around the difference between server-side code and client-side. Browse through the JavaScript tag on Stack Overflow and you'll come across more than you can shake a stick at. Many people (either due to willful ignorance or a sad gap in their education) write functions like:

    function getTime() {
      <?php return time(); ?>
    }

It's not at all improbable that somebody told them their site was vulnerable to SQL injection, so they took a brief glance at the Wikipedia page and said, "I know, I'll just stop people from writing this stuff." So they open up the page where people might be entering the malicious text and write some code that will stop them. They run it in their browser and it works — none of their SQL strings make it through. They have now fixed the problem, as far as they are concerned, and the site owner doesn't know enough to tell them how utterly braindead their approach is.