I don’t read chance me threads. I also don’t think whether random people on the Internet are good at predicting admissions decisions has much relevance to whether admissions are unpredictable.
Skimming through the thread, I see that he was accepted to all 5 of HYPSM (M via waitlist). If the decisions were really random and unpredictable, we wouldn’t see that degree of correlation between admission to 5 of the most selective, lowest admit rate colleges in the United States. We could estimate ratings ranges in each of the Harvard admissions reading rating score categories mentioned in the lawsuits, and based on those ratings estimate range of chance of admission and standard deviation (accuracy) of that chance estimate. However, I see little point to go through this exercise, given that he was accepted, which seems to meet the expectation Similarly he was accepted to the other colleges that have been named in this thread (Stanford and MIT), so little point in discussing those cases in detail.
The more interesting cases would be the unexpected decisions. Why wasn’t he accepted everywhere? For example, why was he rejected by Cornell, which is often thought of as the least selective Ivy when he was accepted to HYPSM + Penn + Brown, which are all generally thought of as more selective.
I haven’t looked at Cornell admissions in detail, so I couldn’t tell you much about Cornell admission system besides what is listed in public information, such as their website and CDS. That said, one important factor is that Cornell has widely varying degrees of selectivity among different schools, and likely to a lesser extent majors; while most of HYPSM… do not. Cornell may be less selective as whole than HTPSM…, but the gap is likely much smaller among prospective CS majors. This is an important factor, but is not enough to fully explain or predict the decision in isolation.
Another possible factor is the interview. He says that his first “real interview” was with Brown, and the Cornell one was just for info. This might suggest a weaker interview with Cornell or lack of one. Perhaps with the lack of “real interview”, he was unable to show the non-academic criteria that Cornell emphasizes on the admission page of their website, such as character, involvement, and good reasons for choosing Cornell. Another possible factor is he applied early for Cornell, but not the other schools. Perhaps some of the impressive qualifications where not available at the time of his Cornell application, but were available for others. There are many possible explanations.
I very much doubt that Cornell admission officers are making largely random or whimsical decisions. Instead they most likely have laid out process with numerical ratings in specific categories (both academic and non-academic), like Harvard and Stanford. And admissions decisions can be largely predictable with sufficient knowledge of this process and sufficient information about the application…