Let's take a moment to think about the target audience for toonami.........

hmm....I'd imagine English speaking kids who have very limited experience with japanese culture
Do you think this audience cares how the name "Naruto" is pronounced? No....

In fact, at least half of the people whom I know personally that have watched Naruto pronounce it the EXACT same way as that announcer pronounced it, and they watch the SUBBED episodes. Point is, you learn a trend in pronounciation based on the way words are spelled, and its natural for English speaking folk to place an emphasis somewhere in a word. No matter how its said, the audience as a whole will still twist it to fit their tongue better. Most of us can pronounce it properly because we've been watching the show for several years now. In the first months, however, I mispronounced it just as they did. If you get a narrator and throw a script at him for a series he's never watched before, then he's going to mess it up. And so what if he does? Is it relevant enough to affect the show in any way?