It is frustrating that the article is so coy about the evidence around the premise of the article! But, this website and the youtube video this article is based around both lean more towards pop than investigative.
I could believe even quite a bit younger, there are some wildly talented children and it's easy to believe Michaelangelo to have been one.
Why? There were other talented people who produced masterful works at an early age. From the same time as this there's a Dürer self-portrait, also aged 12-13:
https://en.wikipedia.org/wiki/Self-Portrait_at_the_Age_of_13
> We don't have any really reliable records from that time.
Uh, no. There's no documented attribution of that painting to Michelangelo; that doesn't mean that other things weren't reliably recorded.
Source: know how to draw really well.
https://www.metmuseum.org/exhibitions/listings/2009/michelan...
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https://en.wikipedia.org/wiki/Michelangelo#Early_life_and_ca...
It seems like this painting would be from his time at Urbino's grammar school. His first apprenticeship started when he was 13. You might expect a renaissance artist to do a lot of work on their master's paintings (detail work, etc.) before ever putting their own name to a canvas, but this is, apparently, Michelangelo doing his own thing before ever being apprenticed.
So, while he likely did paint things before this that didn't survive, it's pretty amazing that this is the work of a kid who has yet to be apprenticed and is just pursuing it on his own with nothing more than the advice of people he was hanging out with.