I turned that feature on, viewed a page in incognito mode, and saw this:
<!-- Cached by Wordfence Falcon Engine. Time created on server: 2014-06-12 05:14:24 UTC. Is HTTPS page: no. Page size: 28023 bytes. Host: http://www.jasondunn.com. Request URI: /left-htc-joined-att/ Encoding: GZEncode -->
I'll see what the next 404 error page shows when it breaks again.