By using Squid you can easily proxy requests using (for example) HTTP_PROXY environment variable, Squid can then be exposed over ssh. Proxying over socks (-D) or every individual website (-L) becomes rather tiresome. Not all programs will be able to do socks proxies but most can do http proxies - http/1.1 over nc can use a http proxy!

I'd say the point is valid though if the only function the tunnel is supposed to fulfil is channelling traffic from and to a web browser.

As far as browsers go, only Internet Explorer lacks SOCKS5 support. And I doubt an office which such stringent header filtering has an IT department that doesn't provide people with proper browsers...

I'd actually argue that an office with stringent and archaic filtering of internet use is precisely the type of office to provide only IE, laden with corporate spyware.