Yeah, that H.264 footnote is a bit confusing.
How so? H264 is becoming the codec of choice for high def content. So, how well your GPU does with it is pretty important. That said it all comes down to where your content is coming from. Stuff you DL off the Internet is not going to be >15 Mbps. Think about it this way: If a 100 minute file is 2GB, that is an average bitrate of ~2.7Mbps. Some of that is audio, of course, but let's ignore that for now. So at an average of 2.7 Mbps, even if your peak bitrate is 5X average you are still under 15Mbps. Now, stuff from a Blu-Ray might well be >15Mbps. Of course if you are ripping from Blu-Ray, you can also re-encode to a format your front-end can easily handle (will take a long time though).