To me a 13 years old is still a kid, teenage or not but it’s subjective anyways I guess.They're stats from databook 2 which covers from chapter 109-244 which is the last chapter of Gaiden. The stats apply to 13 year old Obito and if we take Kid as is stated then Obito falls to 12 at the most and that's me being generous.You must be registered for see images
As for being an adult that's a seperate issue just because you're not an adult that doesn't make you a kid there are many stages in between. Starting with baby, toddler, kid, tween, teenager etc.
I took OP as he said it not as how I thought it would fit, since nobody knows how old Madara was when he woke his MS. We're giving MS to 10 year old if we're pushing it they're 12 at best. That would remove any enhancements(Zetsu body) and conditioning given to Obito by Madara Sama.
That conditioning Madara sama gave Obito put him at a level of capability and intelligence to manipulate Nagato, go onto fight and make Minato into a fodder etc.
If you’re going to use those conditions then there’s no way Madara is going to use the mangekyo effiecently at the age of 12 years old. He was well into his teenage years when he awakened his mangekyo in the first place so he should get the same treatment as the academy days Sasuke we’re gonna assume that Madara was 12 years old when he awakened his Ms.