It's not a question of quality. If you wanted quality, a motivated team of humans still can't be beat.

That's why you may notice that in making AI, companies still use teams of highly motivated humans. Obviously they could have AIs holding the reigns of other AIs. Nothing technical is stopping them

A motivated team of humans is neither necessary nor sufficient for quality, but even if it was there's not enough people for such teams to re-examine all the code; this is because the code that actually exists was made by unmotivated teams at varying skill levels from intern upwards.

  I've seen things you people wouldn't believe,
  a thousand lines inside a if statement's main block,
  an entire pantheon of god classes in a single project,
  something something like tears in rain.

1) They report increasingly using AI to improve the AI.

2) Apples to oranges. The best humans can still beat AI in *AI research, per unit time*, but the AI beat the typical team at *finding exploitable bugs, per line of source, per unit cost*.