60 to 70% accurate?
I'll bet I could categorize left or right at least that well just based on the names of the sites, without seeing any content at all! Since an "AI" can't understand articles well enough to determine political slant beyond word analysis, and has no way of ascertaining factual accuracy unless it has already been told by people some facts to compare with, it all seems rather pointless.
Hyper partisans see themselves as being only slightly left or right of center - they believe they are part of the "silent majority" in the country. Any evaluation of a source as "left" or "right" (let alone "center") will not be accepted by those who most need to be slapped upside the head and told they are an extremist. They judge "facts" based on the partisan news sources they choose (which they don't see as biased) and when the AI judges the truth or untruth of those "facts" differently they'll simply claim the AI is biased and reject it.