[latchkey]

Squid 3.0 was released in 2007. It can be argued that this is an out of date recommendation. My experience using query strings has been fine.

[eli]

To be fair, I think it was still the current version up through 2011.

The more important point is that the failure mode is simply that the assets load from the CDN as if there were no squid proxy. This is not ideal, but it's not so bad either.