> If the PR does what it says it does, why does it actually matter if it took 2 weeks or 2 minutes to put together, given that it's the equivalent level of quality on review?

You're right that the issue isn't how many minutes it took. The issue is that it's slop. Reviewing thousands of lines of crappy code is unpleasant whether they were autogenerated or painstakingly handcrafted. (Of course, few humans have the patience and resistance to learning to generate the amount of terrible code that AIs do routinely).