> In a completely different environment than you're used to, while proctors watch you like a hawk. Your whole future rides on this! is not how I would describe a wholistic assessment.

I would wager that a large portion of Harvard admitted students did not in fact have this as an unfamiliar environment for the first time, but had like a whole year of test prep and simulated tests and took the tests multiple times if they weren't going to get in with their initial result, which could be a money barrier for others.