Actually, when you think about it, it makes a lot of sense. Historically, they interview around 1,000 to accept around 300 to fill a class of around 100. With free tuition, they expect their yield to increase dramatically, but they really have no way to know, because the situation is not static. Other schools are already reacting with better aid packages, and NYU has no way to know whether money will ultimately drive matriculation decisions (wealthy people may decide Harvard or Penn at full price is still a better move for them than NYU for free, needy people may have the same COA wherever they go, schools might match NYU's money to avoid losing candidates they want, etc.).
So, if they have the bandwidth to interview 1,000, why not? It's the number they've seen historically, and it's the number their NY peers see, so why not take the opportunity to meet more well qualified applicants as opposed to arbitrarily eliminating more of them without an in-person meeting? Also, keep in mind they might have to make 100 or more offers off their WL to get their 50 matriculants, so the ultimate number of As might very well be far higher than the 150 you are assuming.
Finally, you have a ton of IIs, so losing one might not be a big deal to you, but most people would much rather have an II with a 1-in-10 shot at an A than not have the II at all, and, of course, anyone is free to either not apply or to turn down the II if they don't like the post-II accept rate!! 🙂