Sony has 13, not 12 (technically 15 if you include their smartphone studio and their global publishing studio, but I don't add those because I don't included MS Casual Games, Lift London or MSGP because of what they do). They're probably forgetting the San Mateo Studio that's supposed to work on Uncharted.
Sony has 7 AAA studios (well it's 8 with San Mateo). Naughty Dog, Polyphony Digital, Bend Studio, Sucker Punch, Guerilla Games, Santa Monica, San Diego, and San Mateo. I personally don't count Japan Studio (mainly collaborations and small teams that work with other studios).
Microsoft's can vary too depending on who you classify as AAA (like Ninja Theory). They are 343 Industries, The Coalition, Playground Games, Rare, Turn 10, Undead Labs, and The Initiative. So Microsoft has 7 or 8 depending on if you count Ninja Theory. Undead Labs is smaller right now, but they're growing in size quite a bit and State of Decay 2 is considered AAA so I included them.
So MS has the same amount of AAA studios currently as them. That'll definitely be surpassed if what we're hearing happens at XO18, and by next year, they'll probably surpass the amount of studios Sony has (MS is currently at 10).