As indicated on the site linked above, it is impossible to accurately age a deer beyond 4 1/2 years. In the far north it is especially difficult as the deer there have a longer cold season, with resultant consumption of more browse (small tree branches) as opposed to green stuff like clover--which wears the teeth faster than deer in more southern climes. If he just looked in the deer's mouth (didn't cut the jaw skin flap) and declared it to be 8 1/2 y/o, then he was just trying to pass himself off as "Joe Hunter The Uber-knowledgeable".
If you want to see a real deer-killin' mofo who is the real deal, get a video by Dan Fitzgerald. He's ugly, wears coke bottle glasses, and is a deer killing machine. HIGHLY recommended if you want to see how it's really done. He's a deer killing fool, but is not likely to be featured on TV. Any of his videos are great, but I especially liked "Fight For The Right" as it features a strong pro-hunting message.