In essence. There's a clash, however: it's nearly impossible to cross the 5GB mark if you're using your iPhone properly. By that, I mean doing anything that can be done straight out of the box. If you jailbreak your iPhone and use it to, say, torrent large files repeatedly, you're on grounds of crossing the 5GB mark. Doing this enough times may or may not have ramifications in regards to your data plan and usage.
The clash comes from the idea of false advertising. Unlimited Date Usage should be just that: unlimited. When, in truth, we have unlimited data coverage... so long as we're using the phone as is. /Unmodified.
