Why does URL Helper support unofficial HTTP header REFRESH?

[eluser]WanWizard[/eluser]
Refresh (along with Set-Cookie and possibly some other proprietary pseudo-headers) were created by Netscape in the very early days of the internet and have been basically (but not quite) standard since then.
Because just about every browser supports it, Refresh is pretty safe to use -- and commonly is. W3C disapproves of them, and wants you to use meta tags instead.

If you would look at code (for example the firefox source), you'll see that the refresh header calls the same code as the meta refresh tag. With the difference that for a header you don't have to parse the HTML, so I personally perfer a header if possible.

Which begs the question: which browser was being used on this client's network? Or, in case of a corporate network, which security measures (reverse proxies, L7 load balancers, application level firewalls) were in place that could possibly interfere with 'non-standard' HTTP headers?