My guess is that a large number of the ticket-holders are opera neophytes attracted by the novelty of this project and hoping for a grand theatrical experience.I missed that on my first pass through the review; a friend called it to my attention. I think it's one of the stupider things I've read recently, especially coming from the chief music critic of the Times.
To start with, why on earth is he guessing? He has enough pull to phone the Times and ask who is buying the tickets to The First Emperor. (For that matter, I could call the Met press office and they'd tell me.) That kind of information would be both interesting and useful to anyone interested in the future of opera and classical music in general.
Second, I think it's a dumb guess. Maybe he's spending too much time with the famously conservative Met audience, but in my experience, it's the people who've been around for a while and are sick of endless iterations of Boheme, Aida, and Don Giovanni who want something, anything, new. I really don't think St. Francois and Doctor Atomic were sold out primarily to neophytes.
Third, if a significant percentage of sales are to opera newbies - or to people who love or care about new music in general - that's great! An expanding audience is a good thing!