What makes you think any existing recent code added to Windows has been reviewed by anyone? This is the company that broke the start menu and the login screen in two consecutive updates.

I've heard some inside stories from microsofties.

They do still review code, but the first wave of layoffs in 2022 mainly hit principal engineers and above because some bean counters said "oh, these are the engineers that are costing us the most per head", so it's kind of the inmates running the asylum now.

And I'll say that their biggest sin was always that their code from the late 90s on was about 20% too clever for their own good. Kind of goes to that classic quip about how how it takes twice your brain power to debug code as it takes to write it, so if you were already maxing out just writing it, then you're not smart enough to debug it. That's half of why features seemed to get a 1.0 release, then get replaced with something rather than iteratively improved (the other half being FAANG style internal incentive structures).

Were all seeing the effects of them clearing house of their weaponized autism that was barely keeping the wheels on the wagon. They do review, but they don't have the ability to do it properly at scale anymore. Which makes rewriting everything even more batshit.

Also the company whose start menu ads made the interface so laggy their "solution" was to just preload the bloat.