About half end at first cut. The rest get read by multiple readers, in a sequence that works. I’d guess Harvard will only start additional reads on about 15-16k.
The external readers won’t generally work a 40 or 60 hour week. Sometimes, depending, not even 20. Only the most compelling kids get to final review. Probably the 6k Harvard has mentioned before. By that point, you have multiple very short summaries all can see. How brutal all that final work is can depend on the region and the rest of the balance the U needs. Not everyone will sit on the final committee.
When you know what a school needs and wants- eg, a level of critical thinking and certain sorts of experiences- it’s easy to look for, in an app. The big shame for bright, qualified kids, is how often they miss the point, think they’re just a natural based on their hs successes, can write any old thing in their app and supp.
The link is iffy because she was a one-timer and admits she didn’t get how to review. And UCB is looking for different points than Harvard.